New strange problem with "reset to default" int the Entry Editor Tab

Hello everybody,
To know if someone else has been experiencing this problem in the last few days.
When I push reset to default in the Entry Editor Tab when you are dealing with Content Model, a new pop-up (warning message) comes. See picture.

Also, when you try to save changes in the content model, it doesn’t work. It will always come back to the same old situation.
I do not have any widgets installed in the environment, and I’m unaware of any configuration panel to check. So the message looks very confusing. Is there a configuration setting? If yes, where? Again I’ve used the Web App quite a lot, and I never had this problem.
I uninstalled all the Apps and created a new content model from scratch, but as soon I saved the content Model, this strange behavior returned.
Any suggestions? How to fix it? Is it a problem with my space or a general bug in the web app?