minivator 950 stairlift moving rail stuck?

Hi, I have minivator 950 stairlift that was working well, but all of a sudden the sliding rail has stopped in the upper position and won't slide down, you can hear the motor for it working but sounds like it has disengaged from the rail. The seat cartridge is working fine up and down, it's just the rail. Any ideas, is there a manual way to release it?