have just helped a friend remodel bathroom in basement, new shower pan, reused and reset existing toilet and vanity sink, all plumbing is hooked to a pump system
and eventually runs into town sewer lines. Shower pan is built up like old one on a 2x8 sub floor with new trap assembly to the pump system so really nothing has changed from before. Homeowner remembers this odor awhile back. Need some expertise as to where odor is coming from