The iPad Mini 2 is the lowest possible processor that can be used with Map Pilot. DJI has added some behind the scenes logging lately that hogs the CPU and leaves less for the actual application.
You can either try it with turning off all other applications at the time of operation or using the Connectionless mode which does not require the app to trigger the camera.
You should be able to see this behavior in the dots being dropped as the aircraft moves.
If neither of these is the case you may want to make sure you are using an empty SD card and a genuine Apple cable. Believe it or not it makes a huge difference.
If you are not happy with how your maps are turning out it is a sign that you need to take your images with more overlap.