Horses dismounting players/disappearing

When riding a horse, every so often it will force the player to dismount. It will then either disappear or be stuck in that position, not moving, and the player will not be able to re-mount it. Rejoining the server puts the player back on the horse and it will continue as normal. Also, lots of server log spam saying Horse <vehicle of playerName> moved too quickly! and this happens during rubberbanding.