desktop wallpaper changes on reboot

hi people ... I'm running an updated Ventura on a 2020 iMac. Every time there's a major software upgrade (OS) or occasionally just on re-boot, I lose all the desktop backgrounds I've chosen for my 7 different desktops. This is quite annoying because of time and thought I give to these choices.

I've looked at other posts asking similar questions, but no one seems to have an answer. Any options besides contacting Apple support? Thanks!