What changes are being made?  There is a bug which is being tracked by Sage (but the cause has not been pinned down yet) that can either wipe out the Account Number field, or make it appear as ****1234. I have also had basically all information in a bank code disappear except the code itself, AND I have had a bank code disappear once.  If it's something like this, it is probably not someone making the changes - it's a bug.

Ah! That is the exact issue we are having actually. The account number was being changed and we couldn't figure out why or who was doing so. We thought maybe somebody was running something that was causing it to change so we were trying to get tracking on that field. 

Yeah, that's what we've all been trying to do - figure out what makes it happen!  ALMOST all of my customers who have reported it are using Positive Pay, but not all, so either that is unrelated, or there is more than one causation point.  The only people that notice either have Positive Pay, Direct Deposit, or AP ACH payments, because that's the only time anyone would pay attention - and it causes failures on those files.

Supposedly this had been fixed with a product update several months ago.  Two of my clients have installed the latest product update and it just started happening again a few weeks ago.  I have updated Sage, but haven't heard anything back from them yet.  Both clients are on 2021.4.