Ran into a frustrating one yesterday on this Prologue quest. For the Bangkorai phase of the quest (rescue Kanzin), the marker initially appeared on Rubble Butte, as it should have. Somewhere on the way to Rubble Butte, however, the marker switched to Bangkorai Garrison's southern entrance. Upon getting to the garrison and entering from the south, the marker stuck on an inaccessible door inside the garrison (the west/southwest one, I think, but it's on the left just before the northern gate). After logging out and coming back a couple of hours later, the marker was back on Rubble Butte. Once I got about halfway to Rubble Butte, it changed back to the garrison's southern entrance again. Kanzin really is in Rubble Butte, however.