Sewer odours inside can show a completely dry catch, fractured vent

https://academy.educause.edu/eportfolios/12410/home/reasons-why-homeowners-trust-plumbers

Drain odours inside can indicate a completely dry trap, cracked air vent, or partial obstruction; Geelong properties with large trees or older sewer lines may need CCTV evaluations to find intrusions and prevent reoccuring smells.