Diana's Q is not hitting targets it clearly should be hitting, and sometimes the skillshot will randomly fizzle out in the arc. Also, the range will sometimes auto extend. Here are some example clips.
https://clips.twitch.tv/AmazonianSillyWitchAllenHuhu (14 seconds)
https://clips.twitch.tv/KawaiiNiceCrabThunBeast?tt_medium=create (16 seconds)
here's a link that showcases this occuring.
On another note,
There is also a bug with her E where targets are pushed / jolted away (like a deformed janna ult) instead of being pushed in. This one is a little bit more rare, but only seems to occur in minion waves for the most part. It's absolutely annoying and has been an issue for 9 months now.
https://www.youtube.com/watch?v=pv_VJa3tNR4&feature=youtu.be&t=5m45s (timestamped at the exact time of bug occuring).
Please look into both of these asap. She feels so terrible to play with both of these, especially the Q bug.
additional Q bug - Q randomly disappears during the cast and will auto teleport to a target.
more clear versions of the bug.