Custom forms belonging to a custom record do not allow editing. The custom record was recently updated with SDF, but its forms would not deploy. The forms need to be edited to accommodate the changes in the custom record. The form will not allow a field to be moved nor will it allow a field group to be changed. No locks are in evidence.

Further testing shows that some editing is being allowed, but many edits are not. Of note, this screenshot shows a series of fields missing the Space Before field. These fields each show up in a new column, even though Column Break is not checked.