Supplier of my tractor has actually provided immediate solution for my subject problem, but I still have a residual quandary.
I have long had issues with connecting one of my side-shift flail mower's hyd' cylinder pipes to one of my tractor's quick connection valves (QCV) - the same one every time. However, day before last, I just could not get the female/male connection to lock - no way! Not being completely educated yet on tractor matters, I ordered a new female QCV, but supplier said "Whoa! - QCVs are very reliable and you probably have a pressure issue". They were right.
Under instruction, I tried depressing the valve-head on the relevant male part (flail pipe) on a hard surface, suitably shrouded to prevent spurts of hyd' oil under pressure: it wouldn't budge! After unscrewing pipe connection to flail cylinder (again shrouded) to release pressure, the valve-head easily depressed and the flail pipe then connected to QCV just as it should. So there has long been a pressure build-up issue despite fact that I always toggle hyd' levers to relieve pressure in tractor/implement hyd' circuit/s before disconnections. I'm thinking it has to be due to temperatures and expansion of oil in flail cylinder (because I can't think of anything else). Today, closed-up temp' inside tractor/flail "garage" (an ISO container) was 41C !!
Any other thoughts would be most welcome!
Also, I can't be unscrewing hyd' cylinder connections every time the flail gets hot (if that is the problem): I tried re-toggling hyd' circuit levers with just one flail pipe connected to tractor with ignition off, but that didn't seem to help. So, is it OK to just connect the other flail cylinder pipe and then, with tractor powered up, give the hydraulic lever a very, very, very brief flick to shift the cylinder piston by a fraction to relieve the pressure on the problematic side of the piston or will that cause problems of another kind?
[I hope that all makes sense from a "distance".]