Yep, that'll do it. So what's happening is you're getting to the trader, the game is going "Ok, the wasteland is now within the active chunk, so spawn the wasteland stuff".
And then, because that stuff is SUPER aggressive, it's running over immediately to ruin your day.
Auger and chainsaw should ALSO be fixed, I think.
And yeah, any non-vanilla gun does that. No idea why, not much I can really do about it either.
When you press F6, look ABOVE the list of entities. There's 3 boxes. I don't remember exactly what they say, but it should be something like From Biome Spawner, From Dynamic Spawner, From Static Spawner.
Make sure From Static Spawner is ticked and THEN spawn the guards. That should make them stay on save.
Or you could just take the loss.

They're intended to NOT respawn to stop folks living in the trader 24/7.