MS Excel 365 - An unexpected error has occurred. AutoRecover has been disabled for this session...

Hello! Hoping to get some advise on the correct solution and maybe this can help someone else as I spent a bunch of time troubleshooting on my own and working with my IT folks, which was useless. I have Excel (Microsoft® Excel® for Microsoft 365 MSO (Version 2111 Build 16.0.14701.20278) 64-bit; this may be outdated slightly but my company manages the updates) setup to open to a blank workbook (under Options -> Start up options, unselected "Show the Start screen when this application starts"), this results in Excel opening Book1; this is my preference. Since the last update from Microsoft (maybe unrelated, but who knows), after the specified time for AutoRecover, a popup warning appears and states "An unexpected error has occurred. AutoRecover has been disabled for this session of Excel." The error is definitely tied to this Book1 upon first opening Excel and happens every time I reopen Excel. I change the AutoRecover time, the error pops up shortly after that time (changed from 10 minutes to 2 minutes and the error shows up after 2 minutes now instead of 10 minutes).

My initial troubleshooting to identify the issue:

• If I open another workbook and leave Book1 open, the error occurs (also this seems to be new since the update...before when I would open an existing workbook, Book1 would automatically close)
• If I open another workbook and close Book1 before the error occurs, it doesn't happen
• If I select the "Show the Start screen when this application starts", the error doesn't occur
• If I select new workbook from the start screen, it is still called Book1, but no error!

Advanced troubleshooting I've already done:

• Searched my C drive and OneDrive for all files Book1*.* and deleted those
• Searched my C drive and OneDrive for all files/folders XLSTART and deleted those
• Searched my C drive and OneDrive for all files *.xltx and deleted those
• Searched my C drive and OneDrive for all files *.xlb and deleted those
• Deleted all AutoRecover files in that folder
• Changed the location of the AutoRecover
• Done two repairs
• Uninstalled and reinstalled Office twice - quite the pain because reinstalled messed up Teams and I had to reinstall that as well
• Tried to save Excel template to C:\Program Files\Microsoft Office\root\Office16\XLSTART\ and C:\Users\####\AppData\Roaming\Microsoft\Excel\XLSTART\

Solution (workaround):

• Save Book1.xlsx to: C:\Users\####\AppData\Roaming\Microsoft\Excel\XLSTART\

This solution did not resolved the issue of Book1 staying open after I open the file I actually want to be working in, so this is a workaround that I can live with for now, but would love any advise on how to get it working correctly. Thank you in advance!