When Coolant gets mixed up with the oil, it gets to all the places like the base , solenoids, check valves etc. At this point the machine becomes un predictable. It needs to be completely cleaned out. We like to go all the way. Each and every spool of solenoid need to be cleaned out.  Every pressure valve need to be inspected.

ALL REBUILDS ARE NOT THE SAME.

I have cases where one solenoid was cleaned and there was a recommendation to send the whole B axis to Switzerland for rebuild at a cost of 65K. The devil is in the detail.