Bought 12.9/2 on 2018.01, have been experiencing this [censored] since mid-2018.06 (just after 11.4 has arrived; I think that the problem is haunting me after the unsuspecting "update ios" tap, I've had 11.3 before). Opened an Apple Support Case, had my iPad diagnosed remotely (along with that strange "turn bluetooth on"), no issues were found. Have been directed to service center (the email says "we're always ready to help", lol). Have been denied RMA because a minor 3mm scratch has been found on the screen (have $30 ready for the super-sophisticated diagnostics).
We've all read about the symptoms: some parts of (or entire) screen become unresponsive to taps when it's "not in the mood" (unable to match the glitches with any internal/external conditions like running some apps, changing settings, connecting charger, etc); sometimes you hold the item keeping your finger pressed against the screen, yet iPad (hence the app) reacts as the finger was momentarily lifted and placed on screen surface again; sometimes you drag something (scroll the map, for example) and iPad starts to pinch/zoom the picture, like a second finger was placed on the screen. All kinds of [erratic behaviour], you know the score.
Having all that, Apple Pencil works 100% flawless, not a single glitch can be experienced. Like for all of us, afaik.
nb: suprisingly decent free app to test this kind of problems (when the touchscreen suddenly loses the finger): "Test Device Multitouch" by "Ferret King Co.,Ltd." -
https://itunes.apple.com/ru/app/test-device-multitouch/id1143529785?mt=8
I was ready to resort to selling my iPad for (I hope) 30% of the original price any buying the new one (3rd gen), but what do I see? People complaining of the same [censored] that's bugging the new 2018/3rd-gen iPads. I was hoping that (buying the 12.9/3) I could lose some money but gain a peace of mind (life's short, after all) but now I'm in complete despair. I do not know of other 12.9 alternatives. I can't imagine my life with a screen that's even 1" smaller (wife has 10.5" iPad, can't look at this teeny-weeny).
Divine entity, help us all. This looks like a complete Apple's fault to provide decent hardware+software solution that Apple's been traditionally proud of (I've been a loyal customer for 10+ years). That's a rant, I know, but still...