DIAGNOSIS Those two metal or plastic strips on the inside top-front of the drum are moisture sensors. They work by detecting the slight electrical conductivity of wet fabric. Fabric softener residue, dryer sheet film, and general lint buildup insulate them, so they "think" the clothes are dry prematurely.
FIX You don't need any special cleaners. 1. Unplug the dryer. 2. Get a rag damp with rubbing alcohol (isopropyl alcohol) or white vinegar. 3. Scrub the sensor strips firmly until they shine and feel smooth to the touch, not gritty or coated. 4. Use a dry rag to wipe them off. Let it air dry for a minute before plugging back in.
IF THAT DIDN'T WORK If cleaning doesn't fix it, you might have a wiring issue to the sensor or a fault in the main control board's sensor circuit. But 9 times out of 10, a good scrub is the cure.
HEADS UP To prevent this, cut down on liquid fabric softener or dryer sheets. Try wool dryer balls instead. Also, make sure you're using the correct cycle—'Auto Dry' or 'Sensor Dry' cycles rely on these strips. If you always use 'Timed Dry,' the sensors aren't even being used.