Often problems with TV reception can be resolved by performing a "double re-scan" (also called a dead rescan or a complete rescan).
Essentially your tuner has duplicate information for OPB channels, and even after performing a new scan it's still confused where to actually locate OPB. A double re-scan wipes the memory of the tuner, basically resetting the system. Here are the steps:
1. Disconnect the antenna from the back.
2. Rescan without the antenna connected.
3. Unplug the converter box or digital TV for at least one minute.
4. Reconnect the antenna; plug the converter box or TV back in.
5. Rescan the converter box or digital TV one more time.