Originally Posted by nealtw
That's just chasing the symptom not the cause
Six GPM over a few hours may remove an animal carcass from the drain for little cost.
Strictly, we should list all the causes from the most likely to the least likely and then come up with ways to confirm/disprove those ideas. If the most likely causes involve the least costly fixes then this will be easy and popular but that doesn't happen often.
I suppose a conically shaped coil spring with spring Outside Diameter = pipe Inside Diameter dragged through the pipe should drag out bones that let water pass. Just don't break the line that does the dragging.
If you pull from the small end and the spring is overstressed it should become smaller in diameter and longer and so release itself, if it hangs up.
This sort of brings up the idea that the smelly section of pipe should be somehow isolated. The OP should know within 24 hours if this has been accomplished.