Hi!

We are flying a DJI Phantom 4 and have used DJI GO and DJI GS Pro with a iphone 7 as the controller. We have flown the same distance 17865.2 meters  at a height of 14 meters with front overlap of 60 % and side of 60% capturing photos every 2 seconds. We are missing hundreds of photos (it is supposed to take 1930 and is only taking about 1,000) and have seemed to have tried everything- changing to pix4d capture, new formated sd cards, different heights, different flight orientations. Even when flying two flights perpendicular nothing seems to be working. We put the photos into photoscan to see what is missing, on the corners in general it is taking okay photos but in the center many many are missing.

Any advice would help thank you!

Are you shooting in JPEG or RAW?
What SD card are you using?

Your height sounds much too low for generating an orthophoto and the overlap values are quite low too.
Try some testing of smaller areas to get things working properly before tackling a big project.