My iPhone 12 mini (purchased March 2021) stops mag-charging after 1 minute 30 seconds

My iPhone 12 mini (purchased March 2021) suddenly won't mag-charge all the way. I'm using the Apple MagSafe Charger with the 20W USB-C Power Adapter. It charges fine for about 1 minute 30 seconds, then just stops. It is not in a case. But it also stops when in an Apple case. I have several Apple mag chargers, in several rooms and at work, that have been working fine for various lengths of times up to a year (one is less than one month old), and it stops on all of them. It charges fine on the cable. Battery health gives no error message or any hint that anything is wrong. Maximum capacity is 86%. It's on Optimized Battery Charging.

Please advise.

Thanks.