Some have reported issues on some iPads when trying to edit a movie with Blueye video files in iMovie. It turns out that the hardware on the iPad is tuned to only accept Apple encoded video files. This is done to get increased performance while editing videos on the iPad by utilizing the hardware better.
However, you can follow these steps in the following workaround if you are experiencing the same issue:
1. Open your "Photos" and find the video file from the Blueye Pioneer drone.
2. Tap "Edit" at the top right corner
3. Cut the video a bit shorter (1 second is enough) with the arrows at the bottom.
4. Tap "Done" and "Save as New Clip"
That's it! You should now be able to open, view, and edit your files in iMovie like normal.