Electric bed drifts down

I recently purchased a toy hauler that has a Lippert Ez bed lift. It's a large booth that turns into a bed and then lifts. It goes up and down ok but it won't go up and stay up unless it's all the way to the top and I place pins in it.
If I just lift it halfway to use as a bed, it slowly drifts downward. I don't see any place for pins or a brake. Can someone assist me as I know nothing about this.
Thanks in advance :)