I'm facing the same problem, "ghost touches".
I bought the used Vollaphone in June 2022 and until mid-2023 it worked properly. Since then the problems have started, first sporadically and now more and more often.
Lately, I can't even answer calls without first locking/unlocking them with the power button, and some calls have already been rejected, with one being sent the sms "I can't answer at the moment, I'll call you back later".
I decided to change the touchscreen to see if it would work. I contacted Vollaphone to buy touchscreen and to my surprise I received the reply that they don't have any parts available for the first version.
I'd like to ask if anyone knows of a phone application like the "xev" programme in Linux distros that allows you to test events when you move the mouse or use the keyboard?