Hi Alter_Ego_UK,
What iPad generation are you using?
This problem can occurr if the CPU power is being driven to the max or the audio data can’t be streamed fast enough from the disk.
The CPU meter in Cubasis 1.3 shows only the workload of Cubasis. In v.1.4 it will show the workload of the whole system for better metering.
You can try reducing the polyphony in the setup window to reduce the CPU workload.