So apparently I have had a glitches game for a while (don't laugh).
I came across a Warhound convoy for the first time today and thought it was a brand new encounter. I then had trouble with the "secure the epquipment" part of the encounter as I had already done that so could not finish the thing.
Turns out they have been in the game since day dot, but I genuinely hadn't seen one until TU5. Any one else had the same issues with them?
I had issues with it if I do it to close the the Mast control point. Just like any supply convoy once you take out the first group of 4 elites another group spawns in and comes after you.
BUT there is an issue. They spawn at the Mast and one of them gets stuck in a locked room and you can't get to him. If you have control of the Mast then friendly NPC's get involved and start taking them out. If it's controlled by and other faction same thing happens. But the bottom line is one guy gets stuck and you can't get him. If you can't take all the groups out then it won't give you a completion.
I usually wait until they get much further away from the safe house and Mast before I go after them. Then I can complete it because the NPC's spawn in a different location. I wait near the little island in the middle of the pond now and hit them when they come by. There is also a little brick building further along the path they follow that you can get up on the roof of. Once you take the first group out they actually spawn in and come out of the building your standing on so you can just shoot them down as they run out of the door.