If i am right this is a very old bug, it is on PWI too
doesnt happen with sundown only, happens at any TP spot but its a higher chance to get it at arch/sundown/silverpool since you TP there more often than others
the only way to avoid the chance of getting stuck is by standing still when you TP (do not TP while walking/moving)
also to get yourself unstuck simply fly or re TP (which wont take any time since tp stones have a very short cd atm)