I noticed that when a group of people enter in an hydraulic lift/elevator often when the last person steps in the lift/elevator has a small but noticeable recoil: the lift goes down a few mm then it compensates. This creates a recoil.
It seems that regardless of the number of persons on the lift/elevator this effect triggers when several people enter the cabin in succession and always happens when the last one steps in.
My hypothesis is that a sensor perceives the increased pressure but does nothing while the pressure is building, instead when the pressure is stabilised because no more person enters it gives a bit of extra oil to the piston and we experience the recoil.
Is my idea correct? Or is there a better explanation?