Yesterday I upgraded my clients Sage 50 Accounting 2021 software to build Build: 28.1.01.0176 or version PTXA2021.1.1

All appeared to be working until the accountant attempted to make changes to one of their customers via "Maintain - Customer Prospects" - when she goes to edit anything in this menu or add something new and then proceeds to click save. We get the following error: 

I have rebooted all workstations and the server hosting Sage. I have performed a data file integrity check as well and no errors were present/found. If I try and replicate the issue in the sample companies it works fine so it appears to be something with the company file but chat support referred me to phone support after they exhausted their KB articles but I couldn't  get through to phone support due to queues.

Not sure if I should just reinstall or pull the company file from backup and reconvert or what.

Any suggestions?