Hi and welcome to EBN!
I'm no expert on this but did just want to say to make sure his bedding is thoroughly cleaned once he pees/poops on it. Because if there's still a scent on it, he will continue to pee there. I know you wash his bedding regularly but using some kind of enzymatic cleaner to make sure all the urine scent is gone may be helpful if you're not already doing that.
Also, you may want to put a treat or two in his bed since dogs won't usually pee/poo in his sleeping area.