apparently this is a known bug which was only known to 3rd tier support
here's the support's response:
"According to the logs I think the issue is a known bug that is scheduled to be fixed in update 2 for 9.5. I have a hotfix available we can try. You'll find the Hotfix using the FTP info below. I've also included instructions for applying the fix. If you'd prefer I assist with applying the fix I can do that as well."
The downloaded hotfix was just this file: "Veeam.Backup.ViSoap.dll" with no other bug identifying info.
After about a week of backups, looks like that fix is holding.