The only manual override for hydraulic slides is if the pump motor fails. With that situation, you use a drill with a 1/4" hex bit adapter stuck into a fitting at the rear of the motor housing to drive it. In your situation, does the pump run and the slide not move, or is the pump dead? If the pump is not working, you may have tripped the manual reset breaker when you jammed it. If the pump is working but you can hear it straining on that slide, it is possible that you torqued the slide out of alignment on the rack and pinion sets underneath. Is the slide currently extended and does it look out of kilter? If you have a slide manifold, do the other slides work (assuming the pump is working). If you can see the ram, is there any visible fluid leaking from it. I don't know if you can "stall" a ram to the point that it bursts a seal or hose, maybe some more learned folks can comment on that.
My lone experience with slide vs. cabinet door is that the door lost and the slide didn't seem to care. But as soon as I heard the pump labor and the door snap, I let off the slide switch. Then I went and changed my shorts.
Unfortunately, the Lippert guides on their website do not address this problem. You may need to give them a call.