I hope the community can help you find some solutions! Since this is your first post, some background would be helpful!

I see you mention two rabbits and one specifically is neutered. Is your other rabbit fixed as well? Both should be fixed so they can get along with hormones causing fights, territorial disputes, and sexual frustration. They’re both young it seems, but it may change suddenly, so if you haven’t already, figure out a separate cage scenario for them.

An unfixed rabbit and recently fixed rabbit will both most likely leave territorial poos because of that territorial instinct. Recently fixed rabbits have a hormonal spike after the procedure which may make territory marking worse sometimes.

A potential for the constant marking can be them trying to mark over each other if they’re sharing a cage.

You want to keep at it with relocating stray poops in the box and wiping up pee and putting that in the litter box. It’s difficult to really monitor rabbits in a cage, so if you can get an xpen and start litter training sessions, this can help. You want to build an association with litter box and going to the bathroom, so have you, rabbit, and litterbox in the xpen and each time the rabbit goes outside the box, move it to the litterbox. It helps to have a sound to make at the same time so if you can’t immediately move the rabbit, the sound can still signal that you’re actions refer to what they did right when they heard the sound.

Now a lot of rabbits have the extreme dislike of being lifted and picked up. If this is the case, try to gently coax the rabbit the box each time. Rabbits don’t understand punishment nor is that ethical for treating a pet, so do your best to lock in the association.