If you give a horse a bridle when it is already using one, the first becomes
what it uses and the second gets "lost" until you take the first one back.
Apparently, this has caused some issues with mount eq vanishing.

At reboot, if you give a mount any mount gear, and it already has that type of
gear equipped, it will drop the one you just gave it and keep the one it
already has. Test it for me, and then let me know which way you think you like
better if you have a preference.

Shinarae Lluminus