I'm getting the following error when calling /delta:
resyncApplyDifferences: Resync required. Replace any local items with the server's version (including deletes) if you're sure that the service was up to date with your local changes when you last sync'd. Upload any local changes that the server doesn't know about.
What it's asking is for seems quite extreme, do I need to wipe out all the items I have and replace them with the server version? I know that the current sync state is fine so is there any way to bypass this error?
Also what's triggering this message? Is there any way to avoid it in the future?
The error content here sounds a bit more severe that it really is. Basically it's saying there is an issue with the delta token and the service can no longer determine the changes to the Drive since your last poll.
If you're 100% sure there are no changes, you can simply reset by requesting a /delta without a token and starting over. If you're not 100% sure, you can compare that fresh /delta with your local files and re-apply any changes required (upload local files missing from the drive, delete files removed from the drive, etc).