580SE Boom circuit issues

I've had this machine for 15 years. The problem was very very slight at first then got worse as the years went by. What it's doing is: The backhoe boom sinks down quickly when in the neutral position. It also sinks down while the boom up function is in use and must be held open while digging or swinging to keep from sinking. The dealer has nobody that has any real experience on anything this old. Geeeze its only 31 years old... So the dealer can only guess at it. Could be anything...

580SE Boom circuit issues

580SE Boom circuit issues