Please do your self a favor, like on my cubase pc, i’l do always every minute a ctrl+ S shortcut.
Make a snapshot on your projects after every important part on cubasis.
And it seems something is wrong with your cubasis installation, i have also a ipad4/64gb. With havy load of audio, midi and effects i get 1-2 sec. For undo operations and 1-2 sec. Lags in reaction of the gui when i jump to another bar.
Maybe your device is some cluttered in the flash store. Maybe it helps you reset your ipad compled.
Jan