Form controls not displaying properly

We just noticed a strange issue with the multi-select form controls for two custom post types. The display on the front end changed spontaneously at some point and was no longer usable (see attached screenshots). We were able to ‘fix’ this by opening and then saving these controls in the post type settings.

We can be testing our forms every day to see if this is happening and then resave so hopefully, you have seen this issue before and can help us make sure it never happens again.