I am also experiencing the crashing problem badly. Happens pretty much all the time after pressing full screen then clicking the back button to exit full screen it crashes instantly. Tested on Samsung S5 (Android 4.4.2) (Adobe Air 14.0.0.110)
This also happens on vimeo iframe embeds too...
**Note when self hosting your own videos using the html5 video tag it doesn't seem to crash anywhere near as easily, but on about the 5th time of exiting fullscreen it did eventually crash.
Can we get some votes on this bug and get it noticed at least, we can't be the only ones that need this fixed. Bug#3836092 - Android App crashes after returning from fullscreen to normal in StageWebView with YouTube content