Bitbucket doesn't always release SCM hosting tickets since version 5.13.0

Summary

In some rare cases, Bitbucket fails to release SSH and HTTP SCM hosting tickets and Git processes are running on the server for a time longer than the timeout.
When inspecting the details of the SCM commands not terminating, they are related to clones.

A restart will reset the ticket count.

Expected Results

Bitbucket will release hosting tickets when necessary.

Actual Results

SCM hosting tickets are not always released.
This can potentially lead to Bitbucket queueing requests and, in extreme cases, rejecting those requests.

One way to identify this is to check for Git commands that have been running since a long time.

Here is an example of such processes:

atlbitb+ 12172 48087  0 Mar26 ?        00:00:00 /usr/bin/git upload-pack /var/atlassian/application-data/bitbucket/shared/data/repositories/5765
atlbitb+ 12173 12172  0 Mar26 ?        00:00:00 /usr/lib/git-core/git-upload-pack /var/atlassian/application-data/bitbucket/shared/data/repositories/5765

In this case, collected on the 28th of March, these processes have been running for over 2 days while the the default timeout value (plugin.bitbucket-git.hosting.timeout.execution) is 24 hours.
Also, there is no CPU usage on these processes.

Workaround

Restart Bitbucket (only the affected node for a Data Center installation) when requests start to queue up or are being rejected.

Solution

Upgrade to 6.0.0, 5.13.5, 5.14.3, 5.15.2, 5.16.1 or above.