I have spent some time crawling around my 5075M - looking for loose bolts, etc. - and noted the exposed mid-shaft between the engine and the transmission.
I'm assuming that the 5085M has a similar configuration. The driveline shaft is arranged between two sliding collars at each end - the transmission on the rear and the clutch housing/engine on the other end.
Because it is exposed, it would be vunerable to entangling with twine, rope, wire, or grass and weeds - IMO.
That may be a factor in the problems currently experienced by some owner's.
AKfish