Thanks for the reply. Yes the hydraulic oil filter was changed when the clutch was replaced.
There is no oil coming out of the release air valve - just air. And again to my knowledge that valve never release air untill I started having these issues.
There is no evidence of fluid leaking from a faulty gasket - and the fluid level has remained constant.
Should I just start by changing the hydraulic oil filter?
thank you Curtis. I'll start on this tomorrow.