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Update:

It's now Tuesday and my iPad has been working flawlessly ever since I gave the screen a good smack on Saturday. Don't know what to think, but it appears that there must have been something loose or not seated properly that slapping it corrected.
 
I’m going through this too. Makes apps like Procreate almost useless. I’ve not found a fix either, just noticing more and more how much it’s interfering with everything I try to do with the iPad.
 
Our 2015 gen 1 12.9s had horrible problems on some of 11.x releases but have been great on 12. I notice some software such as Apple news and I think safari might have memory problems that tie up the machine so I often close them and the issue gets mostly resolved. Dry fingers are also a problem for us in the winter.
 
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