[Mom of 2 Beagles]

Is it the kitchen that he normally pees? And his favorite place is to pee on the side of the trash can? What if you picked up the trash can? Put it in a closet or out of his site. The trash can may have scents inside it that draws him to pee on it. How about if you get a new trash can? Then all the scents that he is returning to will be gone. I know you are cleaning it, but seems like you can't ever get it all.

We used to limit their water drinking in the evenings.

Also if you are able to pin down 99 % of his accidents between 9 - 10:30 p.m. I would keep a eyeball glued to him during that period of time.