I know you asked a question, but more information is needed.
When you say overfill, how over the full are you saying? A little over fill is not a big issue. However, if the tank is topped off, then you could have issues. The tank needs air space, as when various cylinders are operated the tank level will go up and down. Check your sight glass and lower the oil level if needed.
Was your hydraulic filter restriction lamp active on the instrument cluster and alarm sounding when cold? That would be normal if you are attempting operate with cold oil, but should go off after you warm up the vehicle. If you have slow hydraulics and no alarm with warm oil, then what oil did you use?
I believe the specification for hydraulic oil on a 580K is Case TCH oil. As Mike as stated, oil weight makes a big difference and you need to insure the oil you used meets the proper specification.