Here is an update.
I called Dewalt, explained the problem and they wanted me to send it to their repair center or take it to a local authorized repair center. I did the later. The local place was skeptical that it would be a free repair because it was 14 months or so since the purchase date. “We’ll see” they said.
While I was waiting I did a bit of research on the parts involved and found that there is a new version of the motor assembly. This says that they made a few changes probably due to issues. I purchased a second trimmer “Bare tool” style for 99 bucks since I missed the first one and my elderly mother kept asking me when the trimmer would be fixed so she could borrow it. (This is why cordless yard tools exist… no hassle for older people). The new one arrived and I noticed it had the new design. I gave it to her as a gift to go with the 20v blower I had already gifted her (and which she loves). A couple weeks ago my repair center called saying my trimmer was ready to be picked up. No charge and it has the newer motor assembly.
Both are working well. We each have one to keep at our own places so mom does not have to haul mine back and forth.
Hopefully the redesign has fixed any issues they have had with the motor.