thanks for the quick responses!
Robert: the seals are all on the door side and appear brand new; I also checked under the pressure plate, all looks great, no crumbling/fraying/anything...
Dustin: the only other suspect I can think of here is this, marked with blue arrow:
-- it looks much brighter in the picture because I had to put a desk lamp directly over it, but the interior matte material does leave an black metal edge like this. It, however, appears to be like that by design / since manufacture -- double-checked the ebay shots of the same model, and they all have it like that.
Not even sure how to test it to maybe further narrow down the problem. (Is there a simple way to make this bit more matte to eliminate that?)