So I'm not sure if maybe this could be an alternative explanation, but I used to use the charging pad integrated into the base of my HP ENVY 32 AIO, and with my new iPhone 12 Pro Max it no longer charged reliably, constantly disconnecting and reconnecting, while the charging light blinked orange.
And this is where a possible explanation comes in, that maybe is the cause of malfunctions with other chargers as well. Because when I read the explanation for the blinking light on the HP charging base, it said the following:
"Blinking amber: Metal object detected around charging area. Not charging."
So it seems that the MagSafe ring is what stops the charger from working, as it has a build-in security 'feature' to stop it from, I guess, heating up metal too much. Therefore charging any iPhone with MagSafe is no longer possible, unless, maybe, because now and then it DID still work, you place the phone juuuuust so and the distance to the ring surrounding the coil is acceptable to the charger.
Either way, is seems that Apple's claim that the new iPhones will still work with all existing chi chargers unfortunately is just not true. :-(