Is he neutured? If not maybe he wants to mark his territory or something
Or get a bigger litter pan? One that includes the area he is peeing on currently?
My female rabbit Acrylic likes to pee in this one random spot along the side of my room (she’s free run in my room) so the litter box is just kinda sitting there but since its not a corner sometimes I come home and one of the buns moved it (easy to move without the corner suppirt) and Acrylic continued using her favorite spot, right on the carpet next to the moved litterbox
So maybe he just really wants to pee in the middle of the area instead of by the corner? Acrylics a rescue too so I dunno if it’d be similar
Or try different litter or forget the litter and fill it with extra hay so he can happily munch while peeing?
Orrr…. Maybe his water is to close for comfort to his litter and he feels like peeing outside of his litter box gives a less likely chance to poision the water?
That’s it that’s all I can think of. Hope you can figure something out!