Niagara effect unreliable on many actor instances

Spend all day trying to find out why my effects spawn unreliably. I have a GameplayCue actor which is spawned automatically and attached to the ACTOR once he passes teh area.

GC actor has a test cube and niagara effect inside.

When I spawn multiple mob ACTORs and they enter the area - all GC actors are applied correctly as I see test cubes attached to ACTOR meshes and they stay there for the full lifecycle of GC actor. But niagara effects spawn well for first several actors and then they’re not spawned or spawned on occasion.

I don’t have a clue why Niagara effects behave like this and how I can fix them?
Example video: