There’s a photo showing the sensor location here: AMS HT - How to keep it dry - #8 by user_251696923
Also some user(s?) found the sensor covered by film from the original component packaging… 
There are cracks and gaps around the various connectors on the back and the seam around the entire bottom edge.
Interesting… I’ll need to examine mine more closely! I’m not sold on the lid seal theory either. For all I know one of the plastics in the housing could be more porous than it should be.
-Max