[Zubersoft]

MobileSheets waits 10 seconds after MobileSheets is put in the background or the screen is off before suspending the MIDI communication. This is to handle situations where the user just briefly switched to another app and back, or accidentally turned the screen off. In order preserve battery power, MobileSheets needs to shut the MIDI communication off when the screen is off or the app is in the background for a long period of time. So what you are seeing makes sense. However, MobileSheets generally should just automatically reconnect to the MIDI instrument and then you can resume sending/receiving messages. That works just fine on my tablets with my MIDI devices, so I'm not sure why it's not working well for you with your Korg PA4x. Are you using the default MIDI library under Settings->MIDI Settings->Configure MIDI Connections? If so, please try switching to "Google", then tap the input and output ports for the Pa4x, and test this again. Hopefully it will then work properly for you.

Mike