Does iOS have a transfer/write speed limit?
When any app quits abruptly and you are back at the springboard - that is a crash. iOS is designed to not make a big deal of crashes since most of the time they are temporary and starting up the program again will clean up the error. That doesn't appear to be happening in your case. 

You can confirm it the next time you connect the device to iTunes or Xcode. Xcode let's you look into the engineering details as to why the program is crashing. 

ITunes instead copies the crash report to your ~/Library/Logs/CrashReporter/MobileDevice folder. The first time this happens, you are asked if you want to send diagnostic information to apple. This sort of crash will then be sent in the future. 

You can connect your device, right click on it in iTunes and reset all warnings to get the asking again - that way you can confirm that this is due to the program crashing and not some other cause.