After running the tests in a loop for many hours, I have encountered 2 issues.
The first is an assertion failure in ext2fs that causes the entire system to freeze (#882507). Based on the build log, this isn't the issue in question, but it's definitely a problem (and it made troubleshooting much more frustrating). The second is an exception being thrown due to a call to getcwd() failing. I believe that this is the issue that caused the test failure referenced in the build log. However, getcwd is returning "No such file or directory" but the directory clearly exists, and as such, I'm not sure how this is happening. I'm wondering if this is somehow related to the ext2fs issues, or maybe load-related. I've requested a binNMU for xerces-c on hurd to see what happens.