so what you need to do is delink this from the fps with worlddeltaseconds
You will need to then play with the amount of force as it will now be different.
now that said are you adding force constantly whilst overlapping? or just once?
if just once there should be an issue, if constantly whilst overlapping then you will need to do this.
if you are doing it once then there maybe an issue in you code where it is repeating itself in a loop. But it definatley sounds like an fps issue if it changes based on that.
in the blueprint you want (force x deltaworldseconds) and input that into your add force.
like i said this value will now likely not be correct so play with it til you get what you need (more than likely you will have to increase the force value as you are multiplying it by a value in the region of 0.0167 or similar depending on your fps)