I have not found that "duplicating the offending bot" works. I have a fresh install of Xcode 12.2 beta 2 (now 3) and deleted all bots and rebuilt them from scratch. Still see the issue with fresh bots, from time to time.
Also seeing strangely long build times that seem to stall on "uploading log files"... to itself? I guess? Which eventually completes, but it adds minutes to each integration run.
Also, seeing a weird issue with bots that are instructed to build an .xcarchive after unit tests just refusing to do the work. Nothing in the log, no errors, it just ignores the request to build an archive. Re-run the integration, sometimes twice, and magically Xcode agrees to do what I specified in the bot definition. After that, Xcode 12 seems consistent with providing me with archives
Highly annoying, these intermittent failures.
(Xcode 12.0.1 and 12.2 beta 3 on macOS 10.15.6, both versions of Xcode exhibit all of the above issues)
EDIT: Just noticed OP was referring to Xcode 11. Oddly enough, I never saw OP's issue on Xcode 11 even once, but I see it very often on Xcode 12