importing iPhone photos - missing many photos

I've seen many threads like this but could not find any satisfying answer.

I connect my iPhone to a windows 10 PC.

I use many types of import tools - the native windows, picasa, nikon's, and even browsing manually to the iphone DCIM folder and subfolders.

Non of the methods import many pictures that appear in my camera roll. The pictures do not show up in any subfolder of DCIM.

I do not want to use iCloud!

Is there a reliable way to import all pictures, even those that were saved to the camera roll from whatapp to the PC?

BTW, iPhone 6, ios 11.2.6