I managed to fix this on an ipad 7th gen by:
Disconnecting the battery,
cleaning the connectors with isopropyl alcohol
fitting a &new* digitiser to the ipad(not the same old one).
Maybe I got lucky… the ipad in question has had some frame damage and seems to have intermittent issues (according to the owner FWIW) with charging and screen staying on. today was the first time it had been ghost touching with no digitiser connected, but appears to be fine now.