Low FPS rendering in simple project

Hey, why would a simple 3 object (sprite actor, sprite pawn and camera actor) C++ game, that is fixed at say 120FPS (in project settings), run perfectly fast (8 millisecond ticks as expected) on my Alienware PC, but when packaged up and run on my other 2 PCs, it r-e-a-l-l-y struggles and fluctuates between 20-50FPS on both of them, even though debug shows the ticks receive the correct DeltaTime of 0.008333 seconds in both cases?