I have seen this when working with kone cranes vf's(cranepro in the US) where a button release on long travel would ramp down your s curve to a stop but it should never be, on maintenance on the lift. The common button was also supposed to be a N/O in the safety cct yet now it seems to be a series cct within the direction cct. It would then drop the safety link to the drive and stop the lift dead.