you might try not letting the little stinker in the bed -i am struggling with a 5 mo old puppy who used to go on potty pads 75% of the time and now my little stinker has decided she will go whenever and wherever she wants, in the middle of playing etc-ON MY COUH EVEN! -no sniffing, just goes
regression in my case... but yours, sounds more like he has a smell he is picking up on or something-??????
they are stubborn..... good luck!