Problems transferring pictures from iPhone 6 to PC.

i want to archive all iPhone photos & videos to my PC. I can see the pictures on my phone, but the DCIM folder on the PC only has a fraction of the photos showing, and those will transfer. Those don't show will not. I downloaded Syncios app onto my PC to see if it could see the pictures. ALL pictures show on Synios as available to export, but when all are selected, only a small fraction (the same ones that showed in DCIM) actually transfer. The other 95% of the pictures simply do not transfer. HELP!!