After using the box without incident, our 2-year old neutered male cat Zoli has suddenly started spraying furniture and walls. He was feral until 6 months but has adjusted. It was only recently that we let him out when it’s nice, and the spraying started. There is a super friendly feral who lives outside. He is “friends” with my cat; they play together when Zoli goes out. Zoli is the alpha cat. Could Zoli be marking his territory inside the house? Any other theories? How do I stop it? Any suggestions would be welcome.