If you can find where the infrared sensor is .. what about layers of tape over that -electrical tape or duct tape - masking tape might get dried out and messy - maybe the signal is getting around & between any gaps in the boxes/towels etc??

The manual should show exactly where it is if you can't find it.
or google online for the brand/ model and find the manual that way.

they are usually right on the front, a small smooth section.

That's about the only thing I can think of.