Hi Marco,
Thanks so much for your report!
If the video had sound, it would be a bit easier to follow, but I think the problem is the same or at least very similar to this one: WIP: Nestable Elements: render inconsistencies builder vs front-end - #2 by timmse
I can reproduce it if I duplicate a section (or container) and then delete it: it is removed from the structure panel but remains visible on the canvas, right?
Best regards,
timmse