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.
Just for those who stumble upon this issue before you implement vCard 3 support: I used a regex to remove all the Google Plus profiles from my address book.
Download and back up the vcf file.
Use the regular expression to find and replace by nothing (did this in Geany, but any other reg exp find/replace will do)
Save vcf file, check diff just in case, re-upload.
Did this with ownCloud, and all my contacts seem to show on my device now.
Here’s the reg exp: