I've been trying to chip away at this achievement and it *felt* bugged. Today I snagged some evidence. Basically the NPCs are spawning and not counting towards their respective 'ticks'. Not sure if they're mis-labelled or just not counting at all.
My achievement progress before the encounter (with the encounter in the background)
The NPC name (clearly "Root-House")
My achievement afterwards (Root-House still not ticked)
It's frustrating enough trying to get these RNG achievements when they're working correctly. ZOS please help!