I’m a bit confused by your structure here. Are the NPC’s interacting with You (the player)? Typically the Player interacts and calls Interface events on the other actors.
Also, any logic that modifies an actor should be coded in said actor.
e.g. Set input Mode UI Only should be coded in the character or controller. Not in some other actor.
Oh and please get away from using Get Player Character and Get Player Controller.
If in the character you call Get Controller. If in controller you call Get Controlled Pawn.