Had that bug on default as well. Tried to replicate it but I don't know exactly what to do to make it happen. I know it occurs when hearthling on a sled is using something else (cart/ram/wrecking ball, etc.) and hearthling model is stuck somewhere else but usually not for very long time and not very far.
I've also heard of this previously, but I've been absolutely unable to reproduce it, and I can't imagine what would make the sled differ from other mounts in this regard.
"Object-oriented design is the roman numerals of computing." -- Rob Pike
The way to fix it is to go far away (like 1 screen distance) and back, so a client can re-render graphic. And yes, as you can see we were using carts. I haven't seen this problem without carts