Causes liability?
As a qualified H&Safety risk assessor with 15K hours, mostly jet I feel entitled to an opinion which members may of course accept or reject
It seems to me that MB were obliged to design a seat which performed as nearl as possible to spec. When informed of problems they should rectify them as soon as possible. This seems to cover the shackle situation. certainly in my day JP Victor Canberra etc we were taught to check the "floppiness" of the shackle.
Considering the pins we always placed them in a designated location and I cannot see why an audible warning could not have been installed such that some type specific action would activate it. Say opening the canopy without the pins removed from the flight block, obviously this would not have been infallible but no seat modification would have been needed and the process easily understood.
Perhaps the audible warning could have been repeated to a sounder outside the aircraft that the seat was unsafe enabling linees to co-operate