Problem backing up iPhone photos to Photos app

At any time did you get a notification like this when you connected your iPhone to your Mac via it's charging cable?

I get one after nearly every system update or upgrade. Did you install it?

Give Image Capture a try. With it you can download manually selected photos to a folder on the Desktop or import directly into your Photos library. See if it works for you.

Additionally before the above give this a try: boot into Safe Mode according to How to use safe mode on your Mac and test to see if the problem persists. Reboot normally and test again.

NOTE 1: Safe Mode boot can take up to 3 - 5 minutes as it's doing the following; 

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files

NOTE 2: if you have a wireless keyboard with rechargeable batteries connect it with its charging cable before booting into Safe Mode. This makes it act as a wired keyboard as will insure a successful boot into Safe Mode.

Did your problem ever resolve? I’ve still been able to backup locally, but if it starts to fail, I would love to know the fix.