akerman h10 hyrdaulics

hi i have a akerman h10 used for cutting scrap with a shear, after working the machine for a while or changing the attachment, the machine will not slew, the boom will drop instantly when the lever is let back to neutral. but the dipper, attachment and track work fine.some times if it left over night it will work fine again. the only other time this happens is when a hydraulic pipe bursts on the attachment. any help advice would be highly appriceated