Hey there Jeff,
We understand you get frequent alerts that the location has changed in the Calendar app. We'd be happy to help you troubleshoot this.
Check to see which calendar the event is set to, in case you have multiple calendars. In the Calendar app on the left-hand side, see which calendar is highlighted.
To help isolate the behavior, test in the iCloud calendar, if available, and add an event to see if the same behavior is experienced.
You can also use these steps to move the events to another calendar:
Move events to another calendar on Mac - Apple Support
If the issue continues, test after turning off and back on the Mail account in System Settings > Internet Accounts > [your account] > Mail. Taking this step may help to clear up unexpected behavior with the account.
Let us know if that helps.
Kind regards.