If the pump kept running, then it was probably low fluid.

But it can also be a bad sensor on one of the cylinders that raise the lid, not "telling" the TCM to "change gears" when the cylinders get fully extended. When they do fully extend, sensors tell the TCM that this has happened, and the pump valves switch to:

1) Maintain pressure in the lid cylinders so the lid stay up.
2) Pressurize the cylinders that lower the top.

Sounds to me like the sensors on the lid cylinders are not telling the TCM to "change gears", but it is hard to say without being there.

Check the level of the fluid AT THE POINT IT ALL STOPS WORKING, there should be a partial tank of fluid at that point. I believe it will be over 1/2 full, I'll check when I get a minute and tell you what mine looks like at the particular moment.