Check your shock length then mate.

It sounds like it might be too short at full extension. You alter that by unwinding the plastic ends alittle each end.

I think ideally you want the length set so if you lift the car you have about .5 to 1mm of upward movement from rest with batteries etc. in the car (droop) before the shock is at full extension.

Have i explained that in a way you understand ?? it makes sense to me but then i wrote it