Electrolux washer dryer's drying cycle just stops after twenty minutes

I have an EWW12753 Electrolux washer/dryer. It automatically stops twenty minutes into each drying cycle, even though the clothes are not dry. There's no error code or anything, it just acts like the clothes are all done and goes into the cooldown cycle. It even does this when I set a dry cycle timer. The washing cycle is completely unaffected.

I've tried cleaning the drain pump, the lint trap, the door seal, and the drum, and this is still happening. I don't think it's the heating element; I haven't opened up the machine yet, but I can still set the heating temperature and as far as I know it still washes hot. My leading theory is now the moisture sensor, but I can't figure out where that's located on this model. (It isn't mentioned in the manual.)

Help?