We will look into what could be causing this. Was it a saved mission or a freshly designed one?
The lagging and freezing has to do with the device overheating (common in the summer) or limited system resources. We recommend having at least an A10 processor as a minimum. Even with that you might need to close other apps to free up system resources, make sure all other drone related apps are fully closed and keep an eye on the temperature of the device.
If you only use the iPad for drone work I would stop applying the large iOS updates to it if you can. Each one takes more and more system resources which leaves less for the apps.