Only when the belt pulley is turning does oil from the right main bearing wind up in the crankcase like it should. Otherwise it just builds up in the first reduction gear case and when you finally do move the tractor after idling a long time, the excess oil tries to all get back into the crankcase thru the half inch hole for that purpose and it all can't fit quick like. That's when it starts to pile up in and around the clutch and some of it gets slung out on occasion. In real bad cases you get wet clutch disks and quarts gushing out - but that's when the light usually comes on and most people start asking questions about the oil shower they just had and eventually find out the proper way to operate these two lungers.
The answer is don't do that. Put the transmission in neutral and engage the clutch to keep that belt pulley turning and returning the engine oil to the engine AS DESIGNED.
You won't find anything in there to repair or tweak to make it any better. There is only a rotating screw type of 'seal' to return liquid oil to the wet side of the clutch system (bearing and gear) and nothing else to do or even replace. A real waste of time going in there to 'fix' something if you ask me, it's NOT broke. The only possible cure might be to remove a bit of trash blocking the oil return hole which would aggravate the situation some. And you could do that from inside the crankcase rather than pull the clutch and reduction gear cover case.