Using older versions of Outlook for Mac for personal email and calendar
I am having this issue as well. I am on Monteray 12.6 (the issue exists for me on my MacBook Pro and iMac). The only way I have gotten it to go away temporarily is to Quit my Apple Calendar App, go into Activity Monitor > Search for anything with "calendar" in it and force quit those actions. Then relaunch the calendar, and everything syncs up immediately. However, it does not stay in sync for long.
Will try upgrading to Ventura today. I'm REALLY hoping this helps. Currently, my calendar invites don't always make it out to people, and if I change the date or time of an event, people don't always get the notification. It's truly a pain in the neck!