diff --git a/docker/test/fuzzer/run-fuzzer.sh b/docker/test/fuzzer/run-fuzzer.sh
index 9a389edc5b2..603c35ede54 100755
--- a/docker/test/fuzzer/run-fuzzer.sh
+++ b/docker/test/fuzzer/run-fuzzer.sh
@@ -1,5 +1,5 @@
 #!/bin/bash
-# shellcheck disable=SC2086
+# shellcheck disable=SC2086,SC2001
 
 set -eux
 set -o pipefail
@@ -76,7 +76,10 @@ function filter_exists_and_template
     local path
     for path in "$@"; do
         if [ -e "$path" ]; then
-            echo "$path" | sed -n 's/\.sql\.j2$/.gen.sql/'
+            # SC2001 shellcheck suggests:
+            # echo ${path//.sql.j2/.gen.sql}
+            # but it doesn't allow to use regex
+            echo "$path" | sed 's/\.sql\.j2$/.gen.sql/'
         else
             echo "'$path' does not exists" >&2
         fi
diff --git a/src/Storages/MergeTree/BackgroundJobsExecutor.cpp b/src/Storages/MergeTree/BackgroundJobsExecutor.cpp
index f3d957117e8..7c784de9ebb 100644
--- a/src/Storages/MergeTree/BackgroundJobsExecutor.cpp
+++ b/src/Storages/MergeTree/BackgroundJobsExecutor.cpp
@@ -84,28 +84,55 @@ bool incrementMetricIfLessThanMax(std::atomic<Int64> & atomic_value, Int64 max_v
 
 }
 
+/// This is a RAII class which only decrements metric.
+/// It is added because after all other fixes a bug non-executing merges was occurred again.
+/// Last hypothesis: task was successfully added to pool, however, was not executed because of internal exception in it.
+class ParanoidMetricDecrementor
+{
+public:
+    explicit ParanoidMetricDecrementor(CurrentMetrics::Metric metric_) : metric(metric_) {}
+    void alarm() { is_alarmed = true; }
+    void decrement()
+    {
+        if (is_alarmed.exchange(false))
+        {
+            CurrentMetrics::values[metric]--;
+        }
+    }
+
+    ~ParanoidMetricDecrementor() { decrement(); }
+
+private:
+
+    CurrentMetrics::Metric metric;
+    std::atomic_bool is_alarmed = false;
+};
+
 void IBackgroundJobExecutor::execute(JobAndPool job_and_pool)
 try
 {
     auto & pool_config = pools_configs[job_and_pool.pool_type];
     const auto max_pool_size = pool_config.get_max_pool_size();
 
+    auto metric_decrementor = std::make_shared<ParanoidMetricDecrementor>(pool_config.tasks_metric);
+
     /// If corresponding pool is not full increment metric and assign new job
     if (incrementMetricIfLessThanMax(CurrentMetrics::values[pool_config.tasks_metric], max_pool_size))
     {
+        metric_decrementor->alarm();
         try /// this try required because we have to manually decrement metric
         {
             /// Synchronize pool size, because config could be reloaded
             pools[job_and_pool.pool_type].setMaxThreads(max_pool_size);
             pools[job_and_pool.pool_type].setQueueSize(max_pool_size);
 
-            pools[job_and_pool.pool_type].scheduleOrThrowOnError([this, pool_config, job{std::move(job_and_pool.job)}] ()
+            pools[job_and_pool.pool_type].scheduleOrThrowOnError([this, metric_decrementor, job{std::move(job_and_pool.job)}] ()
             {
                 try /// We don't want exceptions in background pool
                 {
                     bool job_success = job();
                     /// Job done, decrement metric and reset no_work counter
-                    CurrentMetrics::values[pool_config.tasks_metric]--;
+                    metric_decrementor->decrement();
 
                     if (job_success)
                     {
@@ -121,7 +148,7 @@ try
                 }
                 catch (...)
                 {
-                    CurrentMetrics::values[pool_config.tasks_metric]--;
+                    metric_decrementor->decrement();
                     tryLogCurrentException(__PRETTY_FUNCTION__);
                     scheduleTask(/* with_backoff = */ true);
                 }
@@ -133,7 +160,7 @@ try
         catch (...)
         {
             /// With our Pool settings scheduleOrThrowOnError shouldn't throw exceptions, but for safety catch added here
-            CurrentMetrics::values[pool_config.tasks_metric]--;
+            metric_decrementor->decrement();
             tryLogCurrentException(__PRETTY_FUNCTION__);
             scheduleTask(/* with_backoff = */ true);
         }
diff --git a/src/Storages/MergeTree/ReplicatedMergeTreePartCheckThread.cpp b/src/Storages/MergeTree/ReplicatedMergeTreePartCheckThread.cpp
index 797d0570fbc..0efa83237ca 100644
--- a/src/Storages/MergeTree/ReplicatedMergeTreePartCheckThread.cpp
+++ b/src/Storages/MergeTree/ReplicatedMergeTreePartCheckThread.cpp
@@ -192,7 +192,7 @@ void ReplicatedMergeTreePartCheckThread::searchForMissingPartAndFetchIfPossible(
     if (missing_part_search_result == MissingPartSearchResult::LostForever)
     {
         auto lost_part_info = MergeTreePartInfo::fromPartName(part_name, storage.format_version);
-        if (lost_part_info.level != 0)
+        if (lost_part_info.level != 0 || lost_part_info.mutation != 0)
         {
             Strings source_parts;
             bool part_in_queue = storage.queue.checkPartInQueueAndGetSourceParts(part_name, source_parts);
diff --git a/tests/queries/0_stateless/01015_empty_in_inner_right_join.sql.j2 b/tests/queries/0_stateless/01015_empty_in_inner_right_join.sql.j2
index 6c13654598e..cdb9d253b9b 100644
--- a/tests/queries/0_stateless/01015_empty_in_inner_right_join.sql.j2
+++ b/tests/queries/0_stateless/01015_empty_in_inner_right_join.sql.j2
@@ -4,25 +4,25 @@ SET joined_subquery_requires_alias = 0;
 
 SET join_algorithm = '{{ join_algorithm }}';
 
-SELECT 'IN empty set',count() FROM system.numbers WHERE number IN (SELECT toUInt64(1) WHERE 0);
-SELECT 'IN non-empty set',count() FROM (SELECT number FROM system.numbers LIMIT 10) t1 WHERE t1.number IN (SELECT toUInt64(1) WHERE 1);
-SELECT 'NOT IN empty set',count() FROM (SELECT number FROM system.numbers LIMIT 10) WHERE number NOT IN (SELECT toUInt64(1) WHERE 0);
+SELECT 'IN empty set', count() FROM system.numbers WHERE number IN (SELECT toUInt64(1) WHERE 0);
+SELECT 'IN non-empty set', count() FROM (SELECT number FROM system.numbers LIMIT 10) t1 WHERE t1.number IN (SELECT toUInt64(1) WHERE 1);
+SELECT 'NOT IN empty set', count() FROM (SELECT number FROM system.numbers LIMIT 10) WHERE number NOT IN (SELECT toUInt64(1) WHERE 0);
 
-SELECT 'INNER JOIN empty set',count() FROM system.numbers INNER JOIN (SELECT toUInt64(1) AS x WHERE 0) ON system.numbers.number = x;
-SELECT 'INNER JOIN non-empty set',count() FROM (SELECT number FROM system.numbers LIMIT 10) t1 INNER JOIN (SELECT toUInt64(1) AS x WHERE 1) ON t1.number = x;
+SELECT 'INNER JOIN empty set', count() FROM system.numbers INNER JOIN (SELECT toUInt64(1) AS x WHERE 0) ON system.numbers.number = x;
+SELECT 'INNER JOIN non-empty set', count() FROM (SELECT number FROM system.numbers LIMIT 10) t1 INNER JOIN (SELECT toUInt64(1) AS x WHERE 1) ON t1.number = x;
 
-SELECT 'RIGHT JOIN empty set',count() FROM system.numbers RIGHT JOIN (SELECT toUInt64(1) AS x WHERE 0) ON system.numbers.number = x;
-SELECT 'RIGHT JOIN non-empty set',count() FROM (SELECT number FROM system.numbers LIMIT 10) t1 RIGHT JOIN (SELECT toUInt64(1) AS x WHERE 1) ON t1.number = x;
+SELECT 'RIGHT JOIN empty set', count() FROM system.numbers RIGHT JOIN (SELECT toUInt64(1) AS x WHERE 0) ON system.numbers.number = x;
+SELECT 'RIGHT JOIN non-empty set', count() FROM (SELECT number FROM system.numbers LIMIT 10) t1 RIGHT JOIN (SELECT toUInt64(1) AS x WHERE 1) ON t1.number = x;
 
-SELECT 'LEFT JOIN empty set',count() FROM (SELECT number FROM system.numbers LIMIT 10) t1 LEFT JOIN (SELECT toUInt64(1) AS x WHERE 0) ON t1.number = x;
-SELECT 'LEFT JOIN non-empty set',count() FROM (SELECT number FROM system.numbers LIMIT 10) t1 LEFT JOIN (SELECT toUInt64(1) AS x WHERE 1) ON t1.number = x;
+SELECT 'LEFT JOIN empty set', count() FROM (SELECT number FROM system.numbers LIMIT 10) t1 LEFT JOIN (SELECT toUInt64(1) AS x WHERE 0) ON t1.number = x;
+SELECT 'LEFT JOIN non-empty set', count() FROM (SELECT number FROM system.numbers LIMIT 10) t1 LEFT JOIN (SELECT toUInt64(1) AS x WHERE 1) ON t1.number = x;
 
-SELECT 'multiple sets IN empty set OR IN non-empty set',count() FROM (SELECT number FROM system.numbers LIMIT 10) WHERE number IN (SELECT toUInt64(1) WHERE 0) OR number IN (SELECT toUInt64(1) WHERE 1);
-SELECT 'multiple sets IN empty set OR NOT IN non-empty set',count() FROM (SELECT number FROM system.numbers LIMIT 10) WHERE number IN (SELECT toUInt64(1) WHERE 0) OR number NOT IN (SELECT toUInt64(1) WHERE 1);
-SELECT 'multiple sets NOT IN empty set AND IN non-empty set',count() FROM (SELECT number FROM system.numbers LIMIT 10) WHERE number NOT IN (SELECT toUInt64(1) WHERE 0) AND number IN (SELECT toUInt64(1) WHERE 1);
-SELECT 'multiple sets INNER JOIN empty set AND IN empty set',count() FROM system.numbers INNER JOIN (SELECT toUInt64(1) AS x WHERE 0) ON system.numbers.number = x WHERE system.numbers.number IN (SELECT toUInt64(1) WHERE 0);
-SELECT 'multiple sets INNER JOIN empty set AND IN non-empty set',count() FROM (SELECT number FROM system.numbers LIMIT 10) t1 INNER JOIN (SELECT toUInt64(1) AS x WHERE 0) ON t1.number = x WHERE t1.number IN (SELECT toUInt64(1) WHERE 1);
-SELECT 'multiple sets INNER JOIN non-empty set AND IN non-empty set',count() FROM (SELECT number FROM system.numbers LIMIT 10) t1 INNER JOIN (SELECT toUInt64(1) AS x WHERE 1) ON t1.number = x WHERE t1.number IN (SELECT toUInt64(1) WHERE 1);
+SELECT 'multiple sets IN empty set OR IN non-empty set', count() FROM (SELECT number FROM system.numbers LIMIT 10) WHERE number IN (SELECT toUInt64(1) WHERE 0) OR number IN (SELECT toUInt64(1) WHERE 1);
+SELECT 'multiple sets IN empty set OR NOT IN non-empty set', count() FROM (SELECT number FROM system.numbers LIMIT 10) WHERE number IN (SELECT toUInt64(1) WHERE 0) OR number NOT IN (SELECT toUInt64(1) WHERE 1);
+SELECT 'multiple sets NOT IN empty set AND IN non-empty set', count() FROM (SELECT number FROM system.numbers LIMIT 10) WHERE number NOT IN (SELECT toUInt64(1) WHERE 0) AND number IN (SELECT toUInt64(1) WHERE 1);
+SELECT 'multiple sets INNER JOIN empty set AND IN empty set', count() FROM system.numbers INNER JOIN (SELECT toUInt64(1) AS x WHERE 0) ON system.numbers.number = x WHERE system.numbers.number IN (SELECT toUInt64(1) WHERE 0);
+SELECT 'multiple sets INNER JOIN empty set AND IN non-empty set', count() FROM (SELECT number FROM system.numbers LIMIT 10) t1 INNER JOIN (SELECT toUInt64(1) AS x WHERE 0) ON t1.number = x WHERE t1.number IN (SELECT toUInt64(1) WHERE 1);
+SELECT 'multiple sets INNER JOIN non-empty set AND IN non-empty set', count() FROM (SELECT number FROM system.numbers LIMIT 10) t1 INNER JOIN (SELECT toUInt64(1) AS x WHERE 1) ON t1.number = x WHERE t1.number IN (SELECT toUInt64(1) WHERE 1);
 
 SELECT 'IN empty set equals 0', count() FROM numbers(10) WHERE (number IN (SELECT toUInt64(1) WHERE 0)) = 0;
 SELECT 'IN empty set sum if', sum(if(number IN (SELECT toUInt64(1) WHERE 0), 2, 1)) FROM numbers(10);