Have you experts ever seen this?

I have created a Form for my own database which functions just fine. I cannot find anything out of the ordinary with its composition; it's much like any other in my Forms collection. However, an odd thing is happening in the Navigation Pane.

The Form opens normally and functions fine when I clique its name. Obviously, this process leaves the Navigation Pane "open" and the strange issue happens when I clique to "close" the NavPane. The fly-out does collapse and it leaves the open Form fully functioning but instead of displaying the usual look of a closed NavPane (vertical bar with arrow at top) it shows remnants of the left portion of the opened Panel which go away once any code is executed on the Form.

Then, while the Form is open, if I extend the NavPane once again, it fails to display anything, even though there are certainly Tables, Queries and Forms within the DB. As a matter of fact, the full interface looks out of sorts. The proper display is instantly restored when I place the Form into "Edit" status.

I apologize for yakking on in so much detail. It looks like an Access application issue which is mildly worrisome. I'm using Office365. All other Forms act in the normal way.

I thought I might take the time to create a brand-new Form with identical controls and source tables but save as a new Form name. Why do I hate doing something again which I'd already done once?

Do you think it worth the effort? Is this likely to alleviate the issue in your opinion? I may just do it tonight.  Of course, it will cost me several mugs of tea and, perhaps, a "yard" of some other expensive fuel.