Server returned '403' ('Forbidden') for update, trying Delete and Recreate instead...

[Nick2253]

I'm having an issue between Outlook and Gmail sync that's creating the following error:

Server returned '403' ('Forbidden') for update, trying Delete and Recreate instead...

In particular, this appears to happen any time I accept events through my Gmail calendar, or add guests to an event through my Gmail calendar (whether through the web interface, or on my phone, etc).

In particular, this creates a huge problem, because anytime that this occurs, the inviter or the guests receieve a cancellation notice from me, even though it still shows everything fine on my side.

If I accept events through my Outlook calendar, this doesn't happen.

As an example, I create an event "Test" on my Google calendar through the web interface. I then invite someone to that event. They will receive the invitation. I then synchronize calendars. Sometimes, it will synchronize just fine for a while, but before too long, I'll get the above error, which will send out the cancellation notices.

I have a debug log for this, as well as the full synchronization report, but because of PII, I don't want to post it publicly.

The relevant (I think) section of the log is reproduced below (with PII replaced; uuuu is my username, and xxxx, yyyy are the respective event numbers):

 DEBUG 2024-05-30 11:55:34,249 [ VSTA_Main] Synchronizer.DataAccess.CalDavDataAccess . MoveNext                       - Updating entity '/caldav/v2/uuuu%40gmail.com/events/xxxxxxxxx%40google.com.ics'
 DEBUG 2024-05-30 11:55:34,249 [ VSTA_Main] Synchronizer.DataAccess.CalDavDataAccess . MoveNext                       - Absolute entity location: 'https://apidata.googleusercontent.com/caldav/v2/uuuu@gmail.com/events/xxxxxxxx@google.com.ics'
 WARN  2024-05-30 11:55:34,490 [ VSTA_Main] onizer.Implementation.CalDavRepository`1 . MoveNext                       - Server returned '403' ('Forbidden') for update, trying Delete and Recreate instead...
 DEBUG 2024-05-30 11:55:34,491 [ VSTA_Main] Synchronizer.DataAccess.WebDavDataAccess . MoveNext                       - Deleting entity '/caldav/v2/uuuu%40gmail.com/events/xxxxxxxx%40google.com.ics'
 DEBUG 2024-05-30 11:55:34,491 [ VSTA_Main] Synchronizer.DataAccess.WebDavDataAccess . MoveNext                       - Absolute entity location: 'https://apidata.googleusercontent.com/caldav/v2/uuuu@gmail.com/events/xxxxxxxx@google.com.ics'
 DEBUG 2024-05-30 11:55:34,901 [ VSTA_Main] onizer.Implementation.CalDavRepository`1 . MoveNext                       - Duration: 00:00:00.4108908
 DEBUG 2024-05-30 11:55:34,907 [ VSTA_Main] Synchronizer.DataAccess.CalDavDataAccess . MoveNext                       - Creating entity 'https://apidata.googleusercontent.com/caldav/v2/uuuu@gmail.com/events/yyyyyyyy.ics'
 DEBUG 2024-05-30 11:55:35,639 [ VSTA_Main] onizer.Implementation.CalDavRepository`1 . MoveNext                       - Duration: 00:00:01.3947682

Edit: may be related to #382, #335