I remember reading in another forum post, there can be issues with the amount of RAM required and the number of emulators ES is loading. There was a recent change to reduce the size of background images to reduce the amount required so you could try upgrading it to see. But you’d expect the problem to get better with the rpi2 since it has more RAM.
sudo ~/RetroPie-Setup/retropie_packages.sh emulationstation install_bin
sudo ~/RetroPie-Setup/retropie_packages.sh esthemesimple