Any attempt of customization of a form using PowerApps, results in an "Edit all" link

Veronique Lengelle, thanks!

Answering your questions:

1) Yes, I'm sure I've saved the changes.

2) I get the same behavior in any new library: once I edit the form (I guess I should call it the default form), the Edit all button on the "simple picture thumbnail view" won't work any longer.

I see these errors in the Console:

I realized that the "default form" that I reach when I go to customized my form with PowerApp has not the same fields I see in the form available when I create the library! Please, does this make any sense for you? Here the form I access when entering PowerApp:

And here the fields I get when I access Edit all in a recently created library:

Please, don't hesitate to ask me for any further information that could help to work out this issue. Thanks for your time!