Again, there's a manual release valve to lower the forks. Located ontop of valve body. Use this to indicate a mechanical or electrical problem. If the mast won't lower this way, mechanical. Any dents in free lift cylinder tube? You stated it drifts enough to lower it. Possibly the valve located in the center of the free lift rod stuck closed due to rust. Never had one drift that much unless a seal, tube issue. Outside secondary cylinder tubes rust and pit due to lack of use. Repair is replacement only. Tubes are bad and won't hold a seal. Mast would drift down only. I believe this issue you have is electrical since you stated it drifts down. Lift circuit solenoids. Try and Loosen just enough the main lift hose to see if it lowers upon release of oil. Oil out and lowers. It's Electrical! Won't lower. Mechanical, cylinder, bearing shims, thrust bearing, mast channel debris etc.