Has anyone had a clogged plumbing roof vent pipe?

I had the same sewer smell problem that came and went frequently for about a year. I replaced the air valve as shown in earlier posts with a NEW one, but that didn't fix it. However, wrapping saran wrap around the air valve temporarily using a rubber band did eliminate the smells! No issues with draining the tank. So now a zip tie holds the saran wrap around the valve. Might work for you too?