guys, i bought a china version opo. didnt root or anything since then. now running on 11.0-XNPH33R. tried to install OTA XNPH38R incremental. failed =( it says installation error status 7.... any idea what went wrong?

p/s: after trying that couple of times, still couldnt get it done... so i factory reset the phone, tried again to install OTA, but failed too...