A random bit of info i discovered and why i've had no crashes on patrol paths in my new mod is how i've been adding them this time round. By no crashes i mean not because the patrol path was bad, if it did crash it was for the usual reasons, crap loadout, wrong ship defined in npcships or factionprop, no faction defined in mbase if it went to a base which are the most common reasons.
So, for me at least, why i've had no issues assuming everything is ok with the ship or ships used in the patrol path, loadout etc, is that i add them one at a time. By this i mean if it has 6 waypoints then labelled 1 1, 1 2, 1 3 and so on, assuming it's the first path for a faction, otherwise, 2 1, or 3 1 depending which entry it is. The trick is you add the patrol path and all it's waypoints, then go and test them. I get a crash everytime i add more than one patrol path, don't know why, don't care. If i add them one at a time, then all is good.
Also you can have more things going on, on the same patrol path, for instance, a trader going from A to B, also you could add a freighter entry onto the same path and that works happily as well and adds variety at least to trading patrol paths. I read years ago that you couldn't do that but that's a load of balls because you can. In fact there are few original vanilla paths that have this