Your definetly stalling the wing. This is when the airflow around the wing is interupted for some reason(or something like that). My edge 540 does it all the time if I yank the elevator too hard in a turn. Theres really nothing you can do about it except not turn so hard. It can be VERY dangerous,so be careful. Its best to set your throws on low rates so that they wont exceed the limit that induces this stall effect. And then just be careful on high rates.