there are a lot of "cat pee" eliminators on the market that are fairly cheap and work very well, I have a formerly lined CF arctic sleep system stuff sack that literally smelled like a bar floor on the sunday of a long weekend party, in other words- a nasty, powerful stale puke and urine smell that wouldn't go away, an overnight soak in it, and then a wash with more completely killed the stench, but after a few weeks it came back- turned out the lining was rotting, So I tried sealing it in a bucket with some acetone, followed by a couple of days to air out, then a good wash in an industrial machine separated the lining from the nylon and POOF no more smell, now I just spray it with nylon waterproofing which is good for a quick dunk but will still penetrate the fabric during an extended soak.
So , you might want to sniff the inside compared to the outside- it could actually be the waterproof coating giving up the ghost.
So , you might want to sniff the inside compared to the outside- it could actually be the waterproof coating giving up the ghost.