Hi there,
So, my pair does this (the slow chase… but never any actual mounting, and nothing ever comes from it… they always end up snuggling right after), but they have always done it, so it doesn’t worry me too much. In your case though, it’s not so much that the behavior itself is bad, but rather the change that I think is worth paying attention to.
The last time they had their falling out, what types of behaviors did you see? It’s possible they might just need some bonding sessions to re-cement things.
Any changes to your household? Maybe a new pet or housemate? Sometimes changes to a bond can be due to a medical problem with one bun. Also, is your female spayed? If not, then that would be the most likely cause.
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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.