Video import only importing a limited number of frames

I am having an issue with ContextCapture importing a 3 frame per second video. The video is 3 minutes long and should be able to get around ~600 frames from the video. 

However, on import I am only getting 74 photos on import.

Does anyone have any idea what the issue may be? The video is 4k, in a fisheye format and the original video format is MP4 (H.265/HEVC).