Sewage system odours inside can indicate a dry trap, fractured vent

https://www.pitchero.com/clubs/eyelsh/news/common-plumbing-leaks-that-you-may-experience-2923600.html

Sewer odours inside can indicate a dry trap, broken vent, or partial clog; Geelong residential or commercial properties with big trees or older sewer lines may need CCTV inspections to find breaches and prevent recurring scents.