There is a small oriface that is installed next to the solenoid valve. It sounds like this oriface is missing. It reduces the water flow through the humidifier when it is working properly. You should be able to disassemble the solenoid fittings to check and see if the oriface is in the water line. For a "temporary" fix regulate the water pressure down by closing down on the saddle valve.
Good luck
HVAC Teacher