Drain odours inside can suggest a dry catch, fractured vent

https://academy.educause.edu/eportfolios/12410/home/reasons-why-homeowners-trust-plumbers

Sewage system odours inside can indicate a completely dry trap, broken air vent, or partial clog; Geelong properties with big trees or older sewer lines may need CCTV examinations to find breaches and protect against reoccuring smells.