There is an unfixed bug in live CRM Online around Server Side Sync with CRM Online and the length of data in the location field as if you have a long string in the location name field, like a URL for a Teams meeting, then it will sometimes not be able to fully load that field into CRM as CRM is capped at 240 characters for the location field, but Exchange can store longer lengths so it get stuck in an update loop every 5 minutes. 

This has been acknowledges as a fault by MSFT and will be fixed in due course.  The workaround in the meantime is to amend the source meeting request (if you can), or Complete the Appointment (if you can) as Completed appointments do not experience the issue.

We also have other scenarios where the appointment is updated every 5 minutes due to a person be listed more than once in the Required field, as CRM will let that Save but Exchange will not so they never stop trying to sync, and therefore update every 5 minutes 24 hours a day.  We are trying to workout how the double entry of a recipient is getting into CRM as it might be one of our custom plug-ins or could be something else like a conflict with another Outlook add-in such as Starleaf which an add-in that we use for our video conferencing in addition to Teams.

Anyone else have any issues of appointments updating every 5 minutes ?