This should be SERVERERROR per docs.

SERVERERROR should trigger one or two more retrys, followed by
a reset to synckey 0 (which is exactly what we need here).
Fix comment; We now support more recent versions.
Output the correct structure for this error.
Log the deleteSyncCache method.
Need empty() here. Fixes losing the bodyprefs during looping sync.

bodyprefs might be set, but be an empty array().
Pass the actual collection array here.
Add 'WP' => 'WindowsPhone' DevType mapping.