I just had the same problem with my Pronto RU950/00 V3.2.
and could solve it with the "cleaning contacts" procedure.

However there seems to be some confusion about "cleaning
the 4 contacts at the top right of the screen" as there
is no connector or open/accessible contacts to clean.
The touch screen is connected through a flexible plastic
foil with 4 copper lanes, running from behind the screen
and which seems to be glued to the metal terminations
on the glass surface of the touch screen. I found it very
easy to restore good contact at the 4 points by puncturing
the 4 spots several times with a sewing needle. And the
screen works fine now. But I have no long time experience!
So I may have to repeat this operation eventually.

There is a lot of good information to execute this procedure
spread over several posts .

Below I tried to join the main pieces, and remember my
disclaimer: I do not take any responsibility of this fix
- you try it at your own risk! And you need some device
disassembly/assembly experience and a torx tool to execute
these steps !!!!

- Remove the 4 torx screws (size T6) at the bottom of
the Pronto;
- Open the case by runing your fingernails in the groove
and pry it open.

- Remove a 5th torx screw on the top of the circuit board
and remove the circuit board from the Pronto casing;
- Take off the green rim round the touch screen. The left
side can be lifted, but the right side needs pressure
towards the outside (near the mute button) due to a plastic
tab that fits in underneath. (reassemble it in reverse
order);
- Puncture de 4 contact spots 3 to 4 times with a sewing
needle, applying good pressure to reach the glass surface;
- Connect the rechargeable battery pack, or reassemble
sufficiently to put the batteries in and test. If no success
try to add a few additional punctures.

It worked at the first attempt for me! Good luck


Thanks to bongiornoa, PeraV, and many others.