I have had the same problem as Matt reports - pressure is high, but gear does not go up. This can only happen if the low side is at the same pressure as the high side. This means a leak from high side to low side somewhere in the hydraulic system, could be any of the cylinders, the dump valve, or the spool valve. I have just finished rebuilding all the cylinders and making new hoses. My pump is at Lancair being rebuilt. I'll report results when the pump comes back.

Note that if the low side is at the high side pressure, opening the dump valve does nothing, just as Matt reported. Same thing happens with mine.

It seems like the only sure fire fix would be to add a second dump valve, from the low side back to the reservoir, only to be used momentarily when this problem happens, as a way to get the gear up. You can close it as soon as the pump starts running.

Jon