Thanks for the follow-up, that definitely clears up my misunderstanding of Mathias' earlier email. I don't have any of the RCs installed at the moment, but if I'm reading the news correctly, I expect that my original issue would be unchanged if I run an RC.
Changing timeouts was one of the troubleshooting steps I tried and timeouts did not appear to be the issue. Since I'm on the 2021 release, I set the timeout to 10000 seconds (~2 hours) rather than setting the value to 0, and the SMT calls in question finished in well under a second, both the successful and unsuccessful calls. No timeouts occur on the default setting, nor when I increase the timeout limit.
Taking that into consideration, I would be happy to hear from anyone whether it makes sense to install and test an RC (or nightly) build. For example, if there are major SMT communication protocol changes other that the timeout handling, then I think testing the latest version would still make sense.
Thanks again everyone for the troubleshooting help,