I have a Moto Z² Play that, over time and from using the included fast charger, had its battery heat up and expand. By this time the display had also accrued some burn-in, so I sent it to a repair shop in my city to have the battery and the display replaced (and was invoiced for replacement of both parts as separate line items). It came back with a normal sized battery, but the display still has burn-in! I suspected that perhaps the shop has failed to replace the display, but when I called they told me that it's a possible issue with the motherboard from the heat it had been subjected to over time. They have offered to replace the display again under warranty for the first repair, so at least it only costs me the hassle of sending the phone in again.
I'm having difficulty being sure if the display is new based on unique scratch marks - there aren't a lot now, but there also weren't a lot when I sent the phone in. It's possible the shop simply polished the glass and I couldn't be sure of the difference.
So my question is, is their claim a load of BS, or is it possible for image retention to be caused by something other than the display panel?