Direct mode crashes at app start in some Android 4 devices

I've noticed that compiling an APK with <renderMode>direct</renderMode> in the app descriptor (or Processing Mode: "Direct" in AIR for Android settings in Flash Pro CS6), results in the app not working at all in some devices.

In a Samsung Galaxy Tab 2 it works fine in Direct Mode, but in two tablets named NVSBL Dragon and Yarvik GoTab Zetta TAB466EUK, it doesn't. All of them have Android 4. After you press the app icon, the screen goes black for 5 seconds, then you get back to the desktop with no error message. This happens every time you press the app icon. I've tried with AIR 3.2 and 3.3 and it always does the same. If the app is in CPU or GPU mode, this doesn't happen.

BTW, I know "Direct" mode is needed for Stage3D, but other than that, I don't really know what's this mode doing. Please, can someone really explain what's "Direct" mode? (so I can begin to understand why it doesn't work in some devices).