Sewage system odours inside can show a dry trap, split air vent

https://online.seminolestate.edu/eportfolios/1186/home/why-you-need-a-professional-plumber-to-clear-blocked-drains

Sewer odours inside can suggest a completely dry catch, cracked vent, or partial clog; Geelong homes with huge trees or older drain lines might require CCTV inspections to locate invasions and stop repeating smells.