Return of sewer smell

Two months ago I replaced the wax ring on a toilet due to a strong sewer smel. The odor went away immediately. However it is now back! Any ideas on why? I don't see any cracks in the porcelain, there is no apparent water leaking and the toilet functions properly. The toilet is late '80s and I replaced the ring with an Oatley reinforced standard size (flange is slightly above floor level). Thank you for any input!!

 

Could be a lot of reasons but one is if the toilet is rocking or otherwise moving, the wax seal could be breached. It doesn't snap back into place, so if it was the seal last time, it may be the seal this time. Simplest explanation first. If the toilet is rock-solid, then maybe something else.