I think this is due to selecting the 'Copy Target Mount" option being checked.

I'm sorry, I don't understand what bug you are trying to report.

I had assumed that only favorite mounts would be summoned when I use the hot key to random summon a mount. Maybe I misremembered and that is not how it works. Turns out I can set priority to zero to exclude individual mounts from being randomly summoned.

That's definitely not how it ever worked. I'm glad you found the solution on your own, good work.

Happy adventuring, X.