The dryer was shutting down mid-cycle via the over-temperature fuse. When I disassembled both the permanent press thermostat AND the high limit thermostat, BOTH had fused contacts. So the dryer was going full-on all the time, with no temperature regulation. When clothing loads were medium-sized the over-temperature fuse would shut it down, with light loads, it seemed to work OK. Had me confused for a while. NOTE: the overtemperature fuse should never trip. If your dryer completely shuts down mid-cycle, "something" is seriously wrong. Best to replace both thermostats and the fuse.
The repair was very easy. Only took 20 minutes to replace the two thermostats and the overtemperature fuse. The drum stays in the machine.. Easy peasy.