I have a custom button that Saves the form and makes a few changes to field values, including a Person.
Everything works beautifully, and has worked for several years. For some time now, when the two users in question open the form, make changes and attempt to Save with a different custom Save button, the user gets this popup error.
The user just removes their name and picks it again and everything Saves properly.
Has anyone else seen this kind of behavior?