Drain odours inside can indicate a completely dry catch, cracked vent

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

Sewer odours inside can indicate a dry catch, split vent, or partial blockage; Geelong residential properties with huge trees or older drain lines might need CCTV inspections to situate intrusions and avoid persisting scents.