Yeah, that just happened to me.
Was running out of Deathholme and attacked the two mobs 'guarding' the entrance when my 4 shamans just decided to run off into the sunset, I repressed my interact button (spammed it even) to no avail, they just kept going aggroing every mob through the 'scar whateveritiscalled' and eventually 3 of them died of Lurzan while one of them kept going pretty far until he hit a wall.
Normally when this happens they come running back when I re-hit the interact button, however some times they come back and instead of adjusting correctly they keep running the other way instead.