diff --git a/etc/tsansup.txt b/etc/tsansup.txt
index 37c69805f..fd4028e0f 100644
--- a/etc/tsansup.txt
+++ b/etc/tsansup.txt
@@ -13,10 +13,6 @@ race:BloombergLP::bdlma::ConcurrentPool::deleteObject
 # attempts to explain why there is no race.
 race:BloombergLP::bcema_Pool<*>::allocate
 
-# Not sure what the problem is here, but tsan can't show the other stack, so
-# there's nothing to look into
-#race:__tsan_atomic32_fetch_add
-
 # Don't warn about using cout from multiple threads
 race:std::basic_ostream<char, *>& bsl::operator<< <*>(std::basic_ostream<*>&, bsl::basic_string<*> const&)
 
@@ -24,11 +20,14 @@ race:std::basic_ostream<char, *>& bsl::operator<< <*>(std::basic_ostream<*>&, bs
 # it makes tsan warn in some cases
 race:BloombergLP::ball::LoggerManager::isInitialized()
 
-# Suppress TSan report in a routine used in bmqimp::Brokersession test driver.
-# It is a benign race in the test driver, but should be looked into at some
-# point.
-#race:TestSession::waitForChannelClose
-#race:TestSession::arriveAtStepWithCfgs
+# Suppress sporadically appearing data race in bmqimp::Brokersession test driver.
+# In TestSession::arriveAtStepWithCfgs() there is a call of queue->setOptions() method,
+# at nearly same time in other thread bmqimp::BrokerSession::onConfigureQueueResponse() calls
+# queue->options().suspendsOnBadHostHealth() method which is detected as data race.
+# bmqt::QueueOptions and bmqimp::Queue classes are not thread safe by design,
+# and bmqimp::BrokerSession::onConfigureQueueResponse() cllback access them in
+# not thread-safe manner, probably also by design, assuming that it will be called again
+# if something is changed. Further investigation is required, suppress it for now.
 race:BloombergLP::bmqt::QueueOptions::suspendsOnBadHostHealth
 
 # Since we use mqbmock::Dispatcher in unit tests, this method does not get
diff --git a/etc/ubsansup.txt b/etc/ubsansup.txt
index 32a6901b5..5f5613957 100644
--- a/etc/ubsansup.txt
+++ b/etc/ubsansup.txt
@@ -1,6 +1,2 @@
-# bmqp::Crc32c carries out misaligned access of Int64 in one of the internal
-# routines, but only on x86/64.  Misaligned accesses are handled gracefully by
-# this hardware, unlike SPARC.  So we simply suppress this warning.  Other
-# option is to update the code, which can be done by someone feeling
-# adventurous.
-# alignment:crc32c1024SseInt
+# UndefinedBehaviorSanitizer suppressions file for BMQ.
+# See details https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html#runtime-suppressions.
diff --git a/src/groups/mwc/mwcio/mwcio_testchannel.h b/src/groups/mwc/mwcio/mwcio_testchannel.h
index 49357b561..05fd0b349 100644
--- a/src/groups/mwc/mwcio/mwcio_testchannel.h
+++ b/src/groups/mwc/mwcio/mwcio_testchannel.h
@@ -248,7 +248,9 @@ class TestChannel : public Channel {
     /// Pops a close-call from those written to the channel (FIFO ordering).
     CloseCall popCloseCall();
 
-    bool      closeCallsEmpty();
+    /// Lock mutex and return `true` if d_closeCalls collection is empty,
+    /// `false` otherwise.
+    bool closeCallsEmpty();
 
     CloseSignaler& closeSignaler();