When running the omnidbcheck -extended its possible to get false negative results if backups are running at the same time especially if it is an IDB backup. For example, the -dc return may show errors due to the fact that the -dc check reads the DCBF's which may be inaccessible due to the backup.
rerun the omnidbcheck -extended again when no backups are running and compare results
should the errors persist open a call with support to further investigate.