Drain odours inside can indicate a completely dry catch, cracked air vent
https://damienprle790.theburnward.com/the-majority-of-regular-plumbing-concerns-in-geelong-households-and-the-very-best-fixes
Sewer odours inside can indicate a completely dry catch, fractured vent, or partial obstruction; Geelong buildings with huge trees or older sewer lines may require CCTV inspections to locate invasions and prevent recurring smells.