The way around this is to completely switch off the iPad. Press and hold the Power switch until the slider control appears and then accept the offer to switch off. The iPad will power down. Now press the Power switch again until the Apple logo appears and the iPad will power up. This power up does a lot of 'housekeeping' and frees up system memory (RAM). It's a shortage of available RAM that causes an app to quit and return to the Home screen.
Tim