That’s such a shame as the issue lies with the screen manufacturer and software developer but because Peugeot does what all other car manufacturers do and buy these parts (and the majority of other parts) from 3rd party companies they don’t have a clue how to fix them and like you said they just give up (Seat had half a dozen attempts at fixing my Alhambra and still couldn’t manage it), in the end I just lived with it for over a year but it wasn’t as intrusive a problem as yours seems to be and it is ruining what is a great car otherwise!
I have read on other threads that some have had the screens replaced and some sort of software upgrade/downgrade that has seemed to fix the problem, maybe your dealer just doesn’t want to shell out for it?