So here is an interesting post that I hope will help someone out with. I'm going to add some keywords in here too that might match what someone is looking for when looking for something along the lines of "Dynamics 365 Finance/Commerce/Supply Chain Form fields overriding:
There was a scenario where, in production, a user was seeing data mysterious change to an old test server and login credentials. The user would continuously need to go into the system and reset the credentials and server IP for the integration to work. We were not sure if it was a person, a batch process, etc.
We found out that the issue was on the form itself, and whenever a user went into that form and made some kind of action such as expanding tabs or right clicking and selecting personalization. It would overide the data on the fields, not in the table itself. The data would only actually commit to the tables when the form was saved.
After a lot of debugging, we found the issue: A Chrome Web browser addin (LastPass). There was an entry that would recognize the form and automatically default data, much like you would if you were entering credentials for a login page or an address.
There were no indicators or form popups indicating that the fields were being auto-populated. They were just occurring which led the original mystery of why this was happening. Very concerning as all you really needed to do to mess up the data was go into a page and make some kind of action, including non-data related actions.
Debug tip if you're seeing something similar: Turn off all add-ins on your browser and see if you can replicate the issue. Or compare if other users are seeing similar issues.