This does sound like hormonal behavior (including the stinky-ness). Are you very certain they are both males and were both neutered? (Neutering is the term for castrating males, spaying is for females). Just asking because sometimes people get rabbits from sources where they might not get correct info (could be told they have a neutered male when infact they have a female).
Have there been any changes in your house hold, such as new pets or people? Sometimes a health change in one bun can also trigger this type of behavior, so it would also be good to have both bunnies checked out.
Occasional mounting is OK and normal in some pairs, but since this is a new change it’s worth making sure there isn’t something else going on.
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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.