My 2 year old neutered bunny girl is really sweet. She has a biiiig 3 floor cage that I built her myself, with a litter box inside it. She uses it just right 
Outside of the cage, she has a litter box on the place she chose to pee: on the corner of the room. She used it right for a year, but suddenly started to sometimes pee outside of the litter box, just next to it. She pees outside the litter box at least once a day. Since I started to clean it with vinegar, she stopped peeing on the same spot, but keep peeing just next to the litter box.
I tried to put objects (tunels, toys), but she just goes on top of them and pees on everything.
The weird thing? It seems like she does this because she enjoys it! Everytime I FIRMLY say no, she just stops and start to do some binkies.
Also, I’ve travelled a few times since she started doing it and I notice that when we come back, she takes a month to start peeing outside the litter box again.
Her litter box is big, and I always leave hay inside. I don’t know what else to do. Help?