OK, this one is weird...I placed some mobs in my dungeon ( Just starting to experiment with this) and when I kill the first one, it automatically puts me in the looting window, even if I killed it with ranged damage or it was killed by my pet...and when I kill the second one, i can't loot it at all.

What the hey?

you probably have a perk or quest that is overriding mob activation.

I know perks can override activation.

It's not activation that's the problem...it's looting(which, yes, is triggered by activation)...I know of no perk that automatically loots the first mob you kill in an area, and then disables looting for subsequent mobs. I have no nonstandard perks on this character (and I haven't even defined any custom perks) - if there was a perk that did this, it would do it for every encounter in the game, not just mobs added in the CK.

Oh, wait...this particular mob DOES trigger an activation when it dies, to propogate activation on the other mob...AHA! guess that's the wrong way to trigger an ambush, or I need to make sure it doesn't send the PLAYER as the activating reference, but itself.