Can't drag and drop widgets into a ui file

I have used qt creator for almost 10 years without problem. A couple of days back, I upgraded to ubuntu 20.23 and almos all works, except for draging wigets into a form. 

I try to drag any widget into any frame, layout, dialog, and the little prohibited symbol appears in my mouse cursor. It is the first time I have ever seen this

I tried rebooting, reinstalling qt creator, deleting configs inside .config and .cache.

Nothing works. Also there is no messages in the console when I start it in the command line