I'm not as familiar with the older systems, but it still sounds like the big lever controls a valve (3-way?) that either sends oil (Hyd fluid) to the cylinder to raise the bed, holds it in place, or opens the system to let the fluid flow back to the reservoir (and lower the body). Maybe that valve was sticking?
At any rate, the more experienced guys can correct me or validate me on this, but I've always been taught to disengage the PTO when done raising the bed - don't let the PTO pump against a closed valve (bad things happen).
