The original left-rear speaker is now the left-front speaker. It appeared to be fine.
I hooked it up to a home receiver and it functioned normally, whereas the original left-front had no woofer (only tweeter) sound. I got rid of the original left-front speaker.
In my truck, the sound from the left front speaker isn’t as noticeable, so the original (L-F) speaker could have been that way for awhile.
SOMETHING has damaged/or (still) overheats the L output.....if you are lucky the output is protected and is tripping from overload and it cools down when you leave it be, and trips or fails again......the most likely culprit is the orig LR speaker......absent that, look for short to ground along the spkr wires on the L side.....if so, it won’t be a dead short, there will be some resistance. I think probably this will end with the realization that the L output is hurt, though, unless it has protection (thermal switch that opens) as some high-end equipment has.....