Refrigerator works but makes popping sound

I have a several-year-old Whirlpool GS5SVAXVA00 side-by-side refrigerator that seems to operate just fine, except that lately it has taken to making a popping sound every 8-10 seconds. It seems to come from the air diffuser on the upper back wall. In the refrigerator side the air vent has cold air that is interrupted when this popping sound occurs. It’s as if there is a door that is tripping on built up ice. I cannot get the cover off the air vent module, so I don’t know what’s in there. The popping sound is almost as loud from the freezer side. I don’t know why it makes this sound, I just know the popping sound is maddening! Please advise . . .