I am working on upgrading one of our older sites that started as a V8 site, that over the years has gone from 8, 10 to 13 and I am now upgrading to version 17.
I am seeing this when I am clicking between pages.
It could be that a property is being updated due to a change in how property values are being stored, so when you open the page something is updating even though you are not doing it explicitly.
Are you able to narrow this down to a particular document type or property? A quick way to test is to create a blank node of one of the affected types and see if the prompt still fires. If Saving/Publishing the node makes it go away then that may be your culprit but the difficulty maybe tracking down which property.
I’d recommend building a new page from scratch, add grid items to it that the problematic page has. Test that it works as expected, then go to History > Rollback and see the raw stored data. You should be able to compare the raw json between the problematic node and the new one and see what the differences are.
If I am correctly when I converted the site to 13 from 10, I think I used the deploy tool. with some bespoke code. The sites been on 13 for about 10 months, so rolling it back to 10 and then doing the update again, is out.
I had this happen with browser extensions like LastPass or BitWarden. If you have extension permissions to “auto fill” logins and forms, they’ll recognize a form field property as something it thinks it should prefill. Check form fields on the page and see if that’s the case maybe?
I would remove/clear out content one property at a time until the errors goes away to narrow it down. Once you’ve got to that point, you can check to see what was causing the issue and check the raw value in the database (ensure you have a backup to refer back to).
It definitely sounds like a content issue from the migration.