Will DAVdroid will continue the sync and download the server version over the top of the conflicting phone based appointment?
Yes, I think it would be enough to ignore the 409 status (like the 412 one) to do so.
I have noted that when I create a task on the server, and when it produces a 409, that task will never sync to the phone unless I completely reprovision the davdroid client.
That’s true – currently, DAVdroid doesn’t know what 409 means so it stops with an error.
In 409 conflict situations, what are the normal responses that are taken by the client and server?
Should I put this issue to Zimbra for their input?
I have only seen 412 so far, but 409 seems to be a valid answer.