Hmmm how long have they been bonded? Sometimes in a newly bonded pair the habits get worse for a while and then gradually improve.
What type of flooring do you have around? Sometimes buns (especially females) will pee on anything soft. I had one bun that could not have any blankets or beds of any kind because she would just pee on them!
If you have soft blankets, beds, etc, I would remove those for now and see if things improve. Low-pile carpets usually don’t cause issues.
Also, I noticed (with that same bun that peed on soft things), that the areas I was cleaning with vinegar started smelling REALLY strongly of vinegar, and I think she was actually re-marking them to mask that smell. I switched to using a carpet spot cleaner with natures’s miracle carpet shampoo and she stopped marking that spot! So you might also try something like that.
Some people also find it useful to send the buns to “litter box boot camp” where you restrict their space for a bit until box habits return, then gradually increase the space.
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The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.