Mail queue remains stuck after flushing and bypassing from the mail queue page

Summary

Mail queue remains stuck after flushing and bypassing from the mail queue page.

Expected Results

When mail queue is stuck, after flushing and bypassing from the mail queue page, mail queue should be able to continue to send out emails.

Actual Results

When mail queue was stuck and after mail queue was flushed multiple times, click on "bypass currently sending mail", mail queue remains to be stuck.

Workaround

Restart Jira.