Others and I are having problems with our local offline USB synchronizing our calendars in the recent macOS versions (started in Ventura) and iP* devices as shown in these links:
https://talk.tidbits.com/t/my-mac-apple-calendar-went-berserk-i-need-help/23878/39
https://discussions.apple.com/thread/254982807
https://discussions.apple.com/thread/254549186
https://discussions.apple.com/thread/254463571
https://discussions.apple.com/thread/254650642
https://discussions.apple.com/thread/254890299
https://discussions.apple.com/thread/254876661
etc.
We reported this to Apple too with our bug reports, but nothing. We don't want to use clouds too.
Thank you for reading and hopefully answering.