We're having problems on our YouTrack instance (InCloud 2019.1 Build 51932). Most attempts to retrieve Bitbucket commits fail with a "The server is overloaded or down for maintenance. Please try again later." message. I think we're able to add a commit about once-per-hour and it will succeed. This is both via the automatic webhook that YT set up, and manually adding a commit to an issue.
It doesn't appear that the Bitbucket service is having any issues according to their status page.
This has been going on for at least a week. Any ideas? Is the message coming from Bitbucket or from YouTrack? Obviously, if the error is coming from Bitbucket, there probably isn't much you all can do about it.