Intact males can spray, but so can does. Most of my bucks do not spray... but I've had a few that "loved" me a little too much and felt that they had to "mark" me whenever I held them. Honestly, I find that puberty has a lot to do with it. As they mature, they usually stop.
Sometimes, changing their location helps.Is henext to another (more mature) buck? Is the girl "next door" flirting with him? Might help to just move him to another cage, if you can.