If your mobile phone is in a certain mode (state) your sync may be incomplete or may fail.
When you sync a mobile phone that is in a state or mode that prevents data from being copied, the sync may be incomplete, or may fail. For example, if you are editing a contact on the phone when a sync is initiated, the information in that contact may not sync properly.
For best results, make sure the phone or other device is in its normal standby mode before trying to sync.