That was my initial reaction too, i.e. an assembly error, whether or not deliberate.
This was in no way "worn" it was at the time a very new mower.
The only reason I was in there was my (obsessive) habit of taking new things apart to reassemble them with grease so that they aren't rusted together when maintenance is needed.
If I had not got the jam a few days later I would have left it "corrected".
Since I have had no more jams since and there are no other problems I will leave it just the way it came from the factory.
I think this is a probability thing, some exactly wrong combination of position during spin down and tilt of the roller with this end of the roller down COULD cause the knives and shackle to flop outwards and jam the next start-up.
It might be one in 10 or one in 10 million, for me it was one in the first two or three (of some unknown number).
My belief is that it is a design fault that (again, in MY sample) can be masked by an unauthorized assembly procedure.
This is not uncommon - sometimes the guys and gals on the line DO fix "engineering's" problems (-:
The design fault could be a miss postitioned knife hanger if a welding jig is not used
for positioning the knife hangers Reg.
The other issue is run up and cycling with a high speed horizontal balancing machine.
If the rotor was balanced prior to the installation of the knives on the knife stations
and not balanced again with the knives and shackles installed prior to assembling the
mower but I think the greasing of the parts may be the issue as you would not have
gotten the mower if this problem exisited and if they had balanced the rotor with the
shackled and side slicers prior to assembly.
The other issue is using grease as the grease is a dirt magnet and will hold dirt and
grass fines.
I do not use any lubricant of any type as they attract dirt and debris and eventually limit
the movement of the shackle and knves over time.
You should only have a very fine grass dust adhering to the rotor, shackles and side slicers
as this also limits the ability of the shackle and knives to fall away as they are designed to do.
EDIT: At most I would recommend using fluid film and only fluid film on the threaded or cotter pinned portion
of a knive hanger(in my case my knive hangers are spring mounted which permits me to dismount the side
slicers and dethatching blades when the gras dust is removed by scraping away any excess that limits the
knive hanger to slde freely within the weldment which holds the knive hanger.
ANY opportunity to use a hot high pressure washer at the car wash will only help the flail mower owner for seasonal
end of year maintanance as it will break up any grass fines adhering toteh mower hood/shackles/knives/pins or bolts.