Relentless Sewer Gas from under toilet

I have had a sewer gas smell coming from beneath my toilet for 2 months. Here is the info:
-no leaks
-toilet is one year old
-new flange
-new wax ring
-all pipes in crawl and attic are tightly sealed and no obvious cracks or leaks
-roof stacks checked
-smell is intermittent
-flange sits slightly above tile
-have had 3 plumber and a home inspector confirm no leaks and proper pipes
-home was built in 2014 and I am only owner
-no other toilets smell


I am desperate to solve the problem. Does anyone have any advice. All obvious avenues have been addressed.

I have a couple of thoughts,

-Does the toilet bubble when any other fixture is run?

-Could it be the sink, or shower in the room? I am also wondering if they bubble or gurgle when anything else is run.

-I would consider pulling the toilet, and installing a rubber test plug in the flange to seal it and wait to see if the smell persists. That would at least isolate it to whether it is the toilet or wax seal, or not.

I would replace the was ring again. A toilet can leak sewer gas and not water from a bad seal.

In a different thread on this forum, for a similar issue, a smoke test was suggested.

A safe type of smoke candle is used to inject smoke into the drain system under slight air pressure.

It should leak out into the house at any openings not properly sealed, the same places where stink would be getting out.

The test often shows that the actual leak or defect was not where homeowners thought it was.

The stink can travel from elsewhere.

Rodents love to chew through plastic. They prefer Jim caps buried behind floors or in walls most of all.
I have seen it many times after smoke test or opening walls.