I ran into a problem with Google Calender. On my device (phone) I saw 'duplicate' events, ie. the same event twice, but in a browser the web version of Calendar showed no problem.
Root cause: renaming a calendar......
Which might mess up already synchronized calendars on your phone...
I manged to replicate the issue, but behavior was not consistent enough. It would not happen all the time, just sometimes... The use of a third party calendar (Business Calendar 2) on my phone may have further complicated matters, that's hard to tell afterwards.
Fortunately the fix is easy. Unfortunately the only way to get rid of the duplicates is deleting them. Note that deleting one of the two events on the mobile phone did not always work. Apparently Calendar (sometimes) got confused as both events appeared to be identical.
Anyway, my fix:
- Open Google Calender in your browser
- Look for all entries belonging to the calendar with duplicate events
- Change the title of those events, for example add a symbol like '>'
- Open Google Calendar on your phone
- Delete all events in the specific calendar that still have the old name
- Change the title of the (no longer duplicated) events back