Hoping someone can solve this mystery because we’ve tried just about everything. I recently moved back into my home that I had rented out for many years and up until now, never an odor issue. There were lots of renovations done. Since then the master bathroom has had a strong sewage odor. The water company came out and tested the water, no issues there. We had put in a new toilet during the reno was but after noticing the odor, we took out the toilet and put in a new ring. We caulked everything up triple. The odor persisted. We then removed the toilet again and discovered that the PVC going into the flange was a little too small. We corrected that issue. No change. Intermittently the toilet has been clogged up. About a month ago sewage backed up into the shower stall. I used drano in the sinks and tubs of both bathrooms and I put a half a cup of Dawn detergent down the toilets and let it sit. That seemed to clear up the clog. Recently the toilet backed up again and the Dawn cleared it again. Then I bought Root Destroyer and used that. Additionally, the handyman got up on the roof and put a 25 foot auger down the vent on the roof. No blockage there. Next he snaked the shower drain. We suspected that some construction debris went down the shower drain and created a lumpy uneven obstacle that waste was getting caught on. He did encounter some resistance but broke it up with the auger. When he left it appeared that everything was flowing smoothly through the main line as we checked it visually. The guest bathroom always smells fine (it shares the vent with the master) but the guest toilet will show slight flushing issues when the master is backed up. No other issues with any other plumbing in the house. He left two days ago after snaking the shower drain and now the smell is worse than ever. When I shine a light down the shower drain it looks as if the water there is stagnant, there is a film floating on top. It appears that the smell is coming from the shower drain. Please help me solve this mystery!