I had replied earlier that I have had this problem off and on since I went to an iPhone 8 (from a 5s) two years ago. It primarily happens when I have a large number (thousands) of photos with videos to upload. This most recent time it took me working in
small amounts, 50-100 pics. I was able to successfully transfer all of them (eventually). After trying a couple of small groups and getting the freeze, I would reboot both the Windows PC and the iPhone to transfer more. I did move the videos by copying
from files, iphone.
I just had to import more photos and videos. The whole process seemed to work smoother and worked on the first try. I had 133 pics and 5 videos including live photos. It worked on the first try. I do not know if the latest Cumulative update helped or
not. I am still on ios 12.4.1 (waiting for 13 to settle down) and Windows 10 build 1903. The PC did update with the 2019-12 Cumulative update so maybe, it is working smoother.
The photos app not keeping track of what photos are new, is an old problem that of course, still persists. I am just excited if the freeze problem is fixed.