It's easy to reproduce this bug.
We have looked into the code of 3.5.6 version, and we found it may be the issue of `workerPool` .
The `CommitProcessor` shutdown and make `workerPool` shutdown, but `workerPool` still exists. It will never work anymore, yet the cluster still thinks it's ok.
I think the bug may still exist in master branch.
We have tested it in our machines by reset the `workerPool` to null. If it's ok, please assign this issue to me, and then I'll create a PR.