Let's collect issues here that only occur with rare (but valid) build setups, or unit test failures that only occur on certain systems (typically things that Jenkins doesn't catch). Primarily these should still be brought up on the developer mailing list (if such issues are closed as MOVED, add those here, too), but if they can't be resolved easily/sufficiently, they could persist as bug reports.
I have one (seemingly rare) test failure: basic/qa/basic_coverage/test_string_overflow_safe.bas From the comments it seems most likely to me that string length is expected to overflow and doesn't. The test file seems to have been added in ef117cad3a13fda0932bd3da6c032f3499eb9069 by mike.kaganski@collabora.com. My system is Manjaro Linux x86_64, kernel 6.1.9-1-MANJARO, shell bash 5.1.16, DE Xfce 4.18.
My assumption seems to have been wrong, it actually most likely overflows unsafely and segfaults (?). Replacing the doUnitTest = "FAIL" with doUnitTest = "OK" changed nothing, to "pass" the test I had to put early return in the beginning of the test.