Finder on Mac does not recognize updated iOS on iPhone (to back up phone)

I have a mid 2019 MBP (OS Sonoma 14.4.1) that I plug my iPhone 13 (iOS 17.4.1) into with an Apple supplied USB-C > Lightning cable to back up my iPhone "to this Mac" (through a Finder window).

I have an external drive that my Backup folder resides on because my internal drive is too small. I have a SymLink set up which works pretty much flawlessly.

From past experience I know my phone will not back up to my Mac if the iOS is not up to the latest.

The last time I went to back up through the Finder "to this Mac", the Finder window told me "A newer version of the iPhone software is available (version 17.4.1). To update your iPhone with the latest software, click Update". So I did and went away. It took an awfully long time but I let it proceed and when I came back in about 3.5 hours, the Finder window was back to normal (the progress bar at the bottom was no longer showing progress, but back to the normal coloured breakdown of space on my phone, the Revert button (whatever that does) and the Apply button.

It did not say the software was backed up but my phone appear to be on and ready for use so I used it.

Next day I went to back up my phone again and the message that a newer version of software is available for my iPhone was there again. I checked my phone and it indeed has the latest software (iOS 17.4.1).

I tried everything, ended up calling Apple Support, got escalated to a couple senior advisors. We narrowed it done to something in my user account ... I switched users and the Finder no longer indicated I need a software update to my phone, and it actually tried back up, but of course failed because the internal drive does not have enough space and the SymLink resides on the other user account.

So that lead me to believe it is a plist file or some other preference file in my user account that is the problem. The Apple senior advisor told me she did not have the list of plist files I could try to throw away (she did not seem comfortable with that level of troubleshooting ... I promised her I would only rename the plist file, not actually throw it out, but she was unable to help me with that, said Apple does not advise people how to mess with their preference files).

If there is anyone out there who knows what the plist file is called that determines what the finder window shows, when iPhone is clicked on in Locations in a Finder window sidebar, I would love to hear both what it is called and where in my User account it lives. The Library, no doubt, likely in the Preferences folder but that's about all I can guess right now.

I guess the other logical step to be would be to recreate the SymLink, but I don't believe it is the SymLink at all, it acts just like it does when one of the devices is not up to date (sits at the progress bar in the back up window for 14 hours without ever moving). Also, if it was the SymLink that was the problem, I am guessing that it would just fail by trying to back up to the internal drive and then ultimately fail because there is not enough room on the internal drive. Also, it is a pain in the butt to recreate the SymLink, I don't have to use Terminal too often so it usually takes me half the **** day to get it to work again. But it has worked flawlessly for many many many backups, like about every 4th day for the past many months. So starting with the plist file sounds way easier, if I can find it.

TIA if anyone can tell me what to look for.