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

https://learn.multnomah.edu/eportfolios/918/home/why-you-need-a-plumber-to-clear-blocked-drains

Sewage system odours inside can suggest a dry catch, fractured vent, or partial blockage; Geelong properties with large trees or older sewage system lines might need CCTV evaluations to locate invasions and prevent repeating scents.