Don't think so but I am no expert in these sort of things. Box is coming out at in a few months for a check over and a new clutch. Will try a recommended oil and see how it goes.
the offroad shop were selling/ repairing un5,he recommended ulx 110,im running it in my weddle,,oil doesn't normally affect selection when hot,,if its only a couple of gears maybe movement or syncro,if its all gears id say its not disengaging,,clutch maybe