How old are the phones? I noticed when I got my new RST in May, that my 3 year old Moto Z4 was struggling. It was working hard to keep up with the demands of AA and the infotainment system. If I had Maps and Spotify going, it was working overtime. Due to all of this, it wasn't keeping up with the wireless charger, and getting hot.
After putting up with countless freezes and disconnects, etc, I finally upgraded to a new Moto Edge+ 2023 and every thing is fine now. It's having no problem keeping up with the demands, stays cool, and the wireless charger keeps it at 100%. My guess is, the old phone was running at 100% to try to keep up and couldn't, and as a result was burning the battery and getting hot.