When teleported to me after completing a Kamasylvia Main Quest, my horse was teleported underneath the building's floor, and would continue to move under the floor when called while I was still inside the building.

(1) Have a horse/mount accompanying you

(2) Get Quest Item "Kamasylve's Light" from Main Quest "[Kamasylvia] The Healing Light"

(3) Complete follow-up Main Quest "[Kamasylvia] The Heart of Kamasylve"

(4) Speak to Quest Target Brolina Ornette to collect rewards

(5) Observe your horse/mount get spawned under the hall floor (only the "PARKING" arrow is visible, or nothing at all)

[(6) Horse can be whistled out of the floor by moving out of the building and then calling]

Reproducable: ???

Video Link:

https://youtu.be/YTHpHahd8Yg