I found a forum post about this message back in 2013, noting that it was fixed in version 5.2.3. I was not using that old of a version but I did update to the latest 5.21 on the website. It didn't change anything.
How would I go about preventing this from happening in the future? I've had it happen before, and I can access the VM via its console and reset the password on both ends. If I'm storing passwords I typically don't also have them written down on any post-its, so external passwords would be more work to recover, (a solid reason for me to quit using a master password if encrypted passwords can just get broken sometimes).