Oil changed filter changed twice - 6306 hours- no issues with flter. Maybe should be changing more frequently ? Machine 18 months old.
This is a busy place and I'm stretched pretty thin.
Checked filter it is fine.
Anyway.... last resort took a brass drift and while activating side shift, tapped on the main control valve and bingo - away she goes. I'm gonna change oil and filter immediately and hope like heck the whole system isn't contaminated !!