Teleporting Merc + Monster AI Issue

[Smoketest]

EDIT:  Occasionally the merc just vanishes completely, and never reappears in the same area.  The portrait is still there, but the merc is not on screen(or map), and doesn't reappear after a few seconds.  Only returning when a wp(or teleporter) is used.  This one happens even less often than the monsters ignoring merc though.
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Just an update to this note.

Sometimes the hireling will remain on the map, but will stand in one spot and do nothing. You can bring monsters to the area and fight them and the hireling will remain motionless. At other times the hireling will simply disappear from the map. In either case, the hireling's portrait remains visible and you can examine it's inventory. However, you will not be able to modify the hireling's inventory while they are in this state.

As noted, taking a portal fixes the problem. As to rarity, it seems to be tied to server latency. Today the hireling locked up several times in a single game session, under very laggy conditions. Everything was warping around on the screen due to lag preventing a smooth flow of positional data to my computer.

Context: 1.10, closed realms, private game, 56k connection, act 3 normal, rogue hireling(fire arrow)