Early on I found a few things about shifting 919s.
Let me rephrase, I found a few things, mostly related to rider, that resulted in duff shifts.
Slow lazy shifting results in more misses.
Crisp positive shifting gets better results.
A bit of lever preload helps huge, and some would say this is correct technique and not cheater technique.
Hard boots that provide no real lever feel at the toe can mess up things, especially if you have just transitioned from softer boots to hard boots.
Check linkage alignment, noting the fulcrum arms should have the centreline of their lengths parallel, one can too easily screw up the overall linkage geometry by poor adjustment and/or being off a spline or two by incorrect location of the splined fit.
It seems the harder the 919 tranny is worked, the better it shifts.
I found my poor technique most apparent on 5-6 shifts, for whatever reason I do not know.