Not really an item that gives much trouble on the fzs1000, for that reason I would risk a second hand one.Bypassed a few Suzuki ones and an old R1, unfortunately I never had an Fzs1000 on apart to see what was inside.
My theory is usually that if something is not working open and see if it can be fixed. You can't break something that's already broken, as the worst you can do is fix it.
If you do decide to open it post a few pictures of the internals.
The R1 has a little pendulum inside it and track day users fill it with silcone to stop the pendulum. A severe enough tank slapper or very quick change of direction like two quick bends in succession can cause it to operate and cut the engine, unlikely to ever happen in normal road use.