Partial Wakelock - Android System *backup* = NO deepsleep/doze mode
I had the same problem, but it occured after I had restored my phone from google backup. More precisely the "backup" wakelock appeared when I unplugged the phone from the charger. Thereafter the wakelock kicked in and remained doing so until I restarted the phone. But whenever I plugged in the charger, the wakelock came back again and another restart was a must-do. 

How did I solved that? I just disabled the "back up my data" under "backup &amp; reset", restarted the phone and enabled the "back up my data" again. At least for now the wakelock has not appeared again.

This was my trick.