Intermittent TSan issue: heap-use-after-free ../kv_engine/engines/ep/src/ephemeral_bucket.cc:301 in operator() (3.3%)

Error signature

ThreadSanitizer issue: heap-use-after-free ../kv_engine/engines/ep/src/ephemeral_bucket.cc:301 in operator()

Details
6 instances of this failure (3.3% of sampled failures):

• Time: 2020-11-26 16:47:15, Jenkins job: http://cv.jenkins.couchbase.com/job/kv_engine.threadsanitizer/job/master/7760/, patch: http://review.couchbase.org/c/kv_engine/+/141022
• Time: 2020-11-26 16:47:15, Jenkins job: http://cv.jenkins.couchbase.com/job/kv_engine.threadsanitizer/job/master/7759/, patch: http://review.couchbase.org/c/kv_engine/+/141021
• Time: 2020-11-26 16:47:15, Jenkins job: http://cv.jenkins.couchbase.com/job/kv_engine.threadsanitizer/job/master/7758/, patch: http://review.couchbase.org/c/kv_engine/+/141020
• Time: 2020-11-25 17:58:06, Jenkins job: http://cv.jenkins.couchbase.com/job/kv_engine.threadsanitizer/job/master/7717/, patch: http://review.couchbase.org/c/kv_engine/+/141022
• Time: 2020-11-25 17:58:06, Jenkins job: http://cv.jenkins.couchbase.com/job/kv_engine.threadsanitizer/job/master/7716/, patch: http://review.couchbase.org/c/kv_engine/+/141021
• Time: 2020-11-25 17:58:06, Jenkins job: http://cv.jenkins.couchbase.com/job/kv_engine.threadsanitizer/job/master/7715/, patch: http://review.couchbase.org/c/kv_engine/+/141020