I appreciate all of the potential scenarios. But none are consistent with the shop's alleged findings. All brakes are fine. No excessive wear. The offending brake was supposedly much over adjusted. But none of this showed up for 1500 miles. Now, just prior to the smoking event, there had been a lot of rain. And the trailer then sat for several days before heading home and encountering the smoking issue. I am wondering if this is a matter of a brake failing to release, a bit but not much over adjusted. In any case, in a few days we will give it a good test. If the problem reappears, all new components will be installed — brakes, bearings, drums. BTW, Dexter now does not plug the brake adjusting ports in the backing plates, There are two of them in each plate and they are left open. We've since properly plugged them.