I had the same problem sometime ago with a different iOS release and new iTunes software. My fix this time around was the same, and it works! I use Windows 10, and an iPhone X & iPad Pro.
Step 1: Go to your target photo folder (which includes all of its sub folders, and DELETE the iPod Photo Cache folder.
Step 2. Perform a sync on your device, but UNCHECK the “Sync Photos” box, when prompted, select “remove all photos from device” (this action will erase everything from your device). Complete the sync.
Step 3: After disconnecting USB from PC, perform a “hard reboot” of phone or pad & restart the device.
Step 4: Begin a new sync, this time, CHECKING the box to “Sync Photos” (this action will result in recopying ALL of your target folders & photos, and can take some time to complete, as it would if you were setting up a brand new device)
Step 5: After all photos and appropriate folders have been recopied during the sync, everything should be just fine & complete as it was before the combination of iOS 11.3 & iTunes 12.7.4 CAUSED this irritating problem!
After performing these fairly time-consuming & irritatub processes, I found that all SUBSEQUENT syncs run just as normally as they had done previously! Personally, I routinely sync between 500-2000 photos & folders, and found that this worked perfectly for me on both my iPhone X & my iPad Pro!! I do hope that this had helped everyone with this issue, Good Luck in getting things back to NORMAL!