Hello, all!
I has same problem with level of bird boss. When i killed she 1st time, nothing happen. I was wait some time and try again. In the 2nd time nothing happened too.
My native resolution of monitor is 3440x1440.
I found resolve of this problem by changing resolution to 1600x1200, and (oh god!!!) i finished level at last
I think this will help same players, who cant finish this level too. Enjoy