Sewer gas leaking into homes from that tpye of device is very common. Venting sewer gas to outside atmosphere is far more reliable.
That is why it is not an approved device in many plumbing codes.
Problems with AAV’s are not “very common”. The use of these devices is not in lieu of vents to the outside. The vent system is designed to relieve both positive AND negative pressures. AAV’s used in conjunction with conventional venting systems simply work. Do they occasionally fail? Sure, but not nearly to the extent that you claim
I figured it was a frozen vent. I tried the roof, but that would have been suicide to try an crawl on that ice skating rink. So I went in the attic with a sawzall, cut the vent pipe and pulled it down through the boot. Think I found the problem……..