Why does iTunes give a read/write error after a seemingly successful iPhone backup?

I'm at my wits' end with this. iPhone 16 Pro 512 GB, about 350 GB full, using iTunes to back up to my PC. I had no issues backing up my previous iPhone 12 256 GB. I have 600 GB free on my C Drive (SSD) where iTunes backs up phones. iTunes runs for hours, shows the progress bar to the end, but after everything seems to be done, it gives the above error. I go look into the folder and it's almost a 300GB backup that seems to be complete. I do not understand why I get a read/write error after all that work. So far, I have tried the following:

Update iTunes

Update iPhone iOS

Shut down both the phone and PC

"Authorized" the PC that I am using through iTunes

Used different cables

Deleted all other backups in the C folder

Used mklink to route the backup to my D Drive (HDD), which has a lot of space

I'm losing my mind. What am I doing wrong?

[Re-Titled by Moderator]

Original Title: Another "iTunes could not backup the iPhone because an error occurred while reading from or writing to the iPhone" issue