580SL series 3? I'll assume you mean 580SM Series 3. We have had a few problems with the mono block valves. But some were a simple fix. The caps on the bottom of the spool are held with 2 screws. We have had these caps shift and stick spools. Loosen the two screws and stroke the spool/lever a few times and see it it stops sticking. If it does release the lever and tighten the screws up again and it should be centered. If that doesn't fix it remove the cap completely and pull the spool out check for scoring. If the spool is scored time for a new valve. NOTE! when pulling the spool out make sure you remove the hydraulic tank cap to release any pressure. Second make sure the function of the spool you are pulling out cannot move. Boom, locked into position, stick in, bucket rolled out teeth towards ground, stabilizers just touching the ground, extendahoe hoe all the way out or locked with pin, machine level park brake on and swing lock pin in.
