Please provide us this information:
- the generation of iPad (1, 2, 3, 4 or mini)
- the iOS version
- the other apps you're using the iSEM in AudioBus with like Cubasis, GarageBand, Auria or whatever
- Please provide us the version of these apps
You can also Optimize the settings:
Stop all other applications from running.
You can do this by double-tapping the home button and quit all other applications.
- In iOS7 this will be done with a swipe gesture of the respective app from bottom to top.
- In iOS6 or iOS5 you need to hold your finger on the app icon until a sign appears which then can be tapped to stop the app from running.
If this does not help, please reduce iSEM polyphony down to 4 or even 2 voices.
You can do this in the iOS Settings app. There's a special "iSEM" section where you can apply this setting.