I said it in the PR, but I'll say it here too -- I really don't have an idea, nor do I have enough knowledge of the codebase to get debugging data. I suspect that partprobe is either getting an error back from the kernel or is throwing its own error, and partx isn't. if I could step through the process and look at a couple things (like, is some partition actually mounted when partprobe runs, which could trigger this?) I would, assuming I've got the spare cycles. I don't at the immediate moment, and especially not to run through the code to try and figure out debugging on my own. Even being told "set debug here, here, and here, then retry the install" would help.

This affected my install. PR submitted with fix above (with very basic testing done successfully) in the link below.