iPhone sync stuck on Step 4 of 5 for many years

When I sync my iPhone through iTunes, it gets stuck on step 4 of 5 "Reading photo library" - the only way to 'move' it along is to open Finder and open both the Photos app and the photo library itself, for each I right click, select "Get Info" then click on the little padlock in the bottom left hand corner unlock it and enter my system password.

If I do this immediately before the sync or when the sync is stuck it will move on to the next step. But I need to do it each time and it's very annoying - it's been this way for years (I think since OS X?).

The iPhone is an iPhone Xs running 15.6.1, the computer is an iMac from 2019 running OS 14.1.2. I am syncing via a genuine Apple cable with USB-C connection to the computer and lightning connection to the phone. I have of course restarted many many many times over the years, reinstalled from backups etc and nothing fixes it. I've also tried deleting the iPod photo cache out of the library with no success.

What else can I try to fix the problem? I'm so sick of it and often don't sync my phone as a result, would love to finally get to the bottom of this. Thanks so much for reading and any ideas