Unable to boot after canceling file level backup

Here’s a somewhat scary issue.

I completed an image backup of my system drive last night, no apparent issues with that. I started a file-level backup that was supposed to backup select directories of two additional data drives. The backup was in the Indexing phase but hardly doing anything, so I attempted to cancel it. UrBackup didn’t respond, so I killed the back end service and tried to restart it. After doing that, my computer became progressively more unresponsive until I couldn’t even get the Ctrl-Alt-Del security screen to show up. I had to force reboot my computer, after which point, it would remain on the Windows boot logo screen with spinning white dots.

I couldn’t get the recovery environment to load either, same result. I booted a Windows 10 PE from a removable disk which seemed to show everything was intact. I ran chkdsk /offlinescanandfix on all internal drives with virtually no issues found. Even then, no boot. I eventually figured out that by disabling the SATA port of my first data drive, my PC will now boot without an issue. If I enable that one drive again, PC will no longer boot. I am completely stumped by this, but I’m concerned that somehow UrBackup caused this.

I’m running the latest versions of both server and client, client being Windows 10 Pro x64 Update 21H1. Any help would be appreciated.