This could happen when you have a large app or when the app uses a lot of memory .. the emulator has its own, limited memory allocation. You can avoid this by making changes in your blocks without connecting to the emulator. Make the changes, then connect to the emulator. As far as I can tell, this is 'normal' stock emulator behavior (Google's free emulator).
I understand there are other emulators available to run AI2 and other Android apps on your PC that have more features and might run 'better.' Sorry, I can not help you with them; do not have one, just aware some developers use them.
Regards,
Steve