What does the "TLV-11 - unrecognized OID" log message mean ?

The TLV-11 - unrecognized OID message simply indicates that the configuration file contains different vendor (or multiple vendor) information in it.

Cable modem configuration files have multiple vendor-specific TLV-11, commonly called miscellaneous OIDs. They tell each brand of equipment how to do specific things for only that vendor. Since the config has multiple brands in it, all modems will report that error. They don't report that error when they see their native vendor info, but will report it during digestion of a config with other VSIF OID in it.

You may see the above notice in your cable modem's log files every time the modem registers it gets the configuration file. It should not affect the cm operation in any way.