Hmmm, not one I have encountered before.
Intermittent faults are always a PITA to pin down. The drying light should only be on when the drum is doing its long clockwise rotation. It should go out as the drum reverses for a few seconds.
I have never had a fault on the selector switch but have changed several PCB's on these. The circuit board is rather expensive though and none of the mainstream repairers of PCB's will attempt to fix this one.
The stats at the back don't usually fail in this way but I have seen the stat located in the top of the door surround cause something similar. A physical examination of the stats looking for signs of burning or loose terminals might be a good idea.
Have you tried it on the timed heat settings?