I have had a simple patrol system working for some time now. 4 markers placed in a cell that are all link referenced into a circle (a -> b -> c --> d --> back to a, repeat) and I have hooked up a guard to the package. This has worked before. Recently, the guard seems to begin the package, and just randomly stop at the second marker for no reason. He does not every begin walking again (even though the package is set to patrol with repeats, targeting the first marker, so it should tell the AI to patrol all linked markers). Once again, this worked up until recently. I have tried it with anywhere from one to ten guards, but they all stop at the second marker. I have also tried everything from console commands to papyrus calls to get them going again, to no avail. Triggering EvaluatePackage yields no movement. Using the ResetAI console command gets them to restart the package over again from Marker A, but they always stop at Marker B again.

Here are screenshots of the package:
http://i.imgur.com/Xbn2x.jpg
http://i.imgur.com/KJEbr.jpg

Any ideas anyone?

Disregard this. Turns out the AI won't even attempt to get close to something if there is no viable path to it. In this case, I had three markers placed on flat ground, and the fourth placed on a slight incline at the top of the hill, which appears to not have a navmeshed path available.