This is not in any way an issue with your Mavics camera. This is an intermittent problem that we have seen with a few maps that generally share the characteristics of not having a large elevation change throughout the map. We are working to resolve the issue but because it is so intermittent it has proven more difficult than most.
To answer your question about the lens on the Mavic. It does not have a fisheye lens. It has a similar Feild of View to the X5 camera. With a slightly wider FOV of 78.8 compared to 72 on the X5. A comparison of all the X series cameras can be found here. One thing to note is that if you do have a longer lens your FOV will decrease. This means it’s a great Idea to fly higher so you can capture more data that can be used during the stitching process. All senses will have an inherent amount of distortion associated with the camera.
Cheers!
ZG