This is a well known issue here in these Apple support communities with NO real fix or solution.
Apple support can only offer “band-aid” solutions to this issue, like removing protective cases off of these defective iPads
This issue, to this day, STILL affects a small, but STILL continuing and growing minority of random iPad Pro and later iPad Air users.
After nearly 3 years of this nonsense, there is still no confirmed real cause and fix/solution from Apple.
NONE!
Getting one of there defective units is very random and one of a handful of issues going on with higher priced, larger scfeen iPad models that has prevented me from purchasing a new iPad Pro or new iPad Air for the past 2-3 years.
Apple and Apple support have no real fixes or solutions to this issue.
If you have a screen protector on this iPad, remove it as the screen protector makes the touch screen and Pencil experiences worse.
There is absolutely no solution/s to these later iPad Pro/iPad Air touch screen issues.
You can contact Apple support via the Get Support link, at the top upper right hand corner of every Webpage in these supoort communities, but your iPad Air maybe too old, now, for Apple to offer any type of free or in-warranty iPad replacement and Apple will ONLY offer “band-aid“-like advice/fixes/solutions to this issue.
Apple support is pretty much clueless to this issue and has NOT come up with a correct or suitable solution to this nearly 3-year old iPad touch screen issue, nor has there been ANY type of recall from Apple.
This is something you probably didn't want to learn, but doesn't change any of the currently known facts.
So Sorry & Best of Luck to You!