SC 8.1.0.32, mysql
If you have a field document (database) in a form you have to enter the fields ‘File Name’ and ‘File Size’ to correspond to your db fields.
When you add or remove fields from your mysql db and do a synchronize table to update the fields in SC the File Name and File Size in the form field document (database) will shift and will show a broken form.
So SC will not automatically adjust the fields. Always check manually the File Name and File Size entries in document (database) field settings.
I would call that a bug because synchronizing the db table should include all db related properties.