You may be cleaning the litterbox too frequently since hes learning. Leave pee and poo in the box so the scent is there, don’t clean it unless you have to, only once/twice a week. Immediately clean the floor if he poos/pees there-so he doesn’t get used to the scent being there-thuroughly clean with vinegar.
Often litter habits are a small tweak that will fix the problem, so think creatively!!!
***My friends rabbit slept in his litter box and peed/pooped everywhere else; Solved the problem: Switched the litter that was in the box to use as bedding, the bedding to the litter box, and moved the box to another corner-perfect litter habbits OVERNIGHT
***I had been having issues since getting Chuck, all three have been pooping/peeing in a three foot diameter around the one of the litter boxes-thought to be territorial.
I went to walmart and got giant shallow storage containers, and put one type of litter in one, one in the other. There hasn’t been a single stray poo or pee since I brought them home on Wednesday.