Old Skool,
Do you have a pic of your 'knurled section'?
It seem quite clear that
IF the device is fitted correctly, the weak part of the device is not quite weak enough to do what it should, safely.
Despite all this attention on a weak link that isn't, at the very least, shouldn't one notice that the lock is on when doing the hyd checks (free movement x2), autopilot check (cyclic orbit) and the trim checks (stick response)?
It would appear that these 4 checks before take off that would/should identify that the lock is on....don't
