Drain odours inside can suggest a dry catch, broken vent

https://canvas.pasadena.edu/eportfolios/4924~6653/home/common-plumbing-leaks-that-you-may-experience-in-your-home

Sewer odours inside can indicate a completely dry catch, fractured air vent, or partial obstruction; Geelong homes with huge trees or older sewage system lines might require CCTV evaluations to locate breaches and stop reoccuring scents.