Sewer odours inside can show a dry catch, cracked air vent

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

Sewage system odours inside can indicate a completely dry catch, cracked air vent, or partial blockage; Geelong properties with big trees or older sewage system lines may require CCTV inspections to locate breaches and protect against repeating scents.