I have an actor that spawns, and every .1 seconds, moves to the changing location of another moving actor.
For some reason, it will randomly stop while on its way, then continue a few moments later as if nothing happened.
(His goal location is a point right above the circle in the front middle)
Could it be because the goal location is being called at the same rate as the moving actor?
So I did some testing and I think that maybe the marker location is going below your terrain. Try adding a couple units to your z value and see if that fixes the problem.