Imagine the following scenario: checkMetadataConsistency begins executing when shards are still database authoritative (i.e., FCV 9.0), but the actual checks are performed after the shard has been downgraded to FCV 8.0—at which point the shard is no longer authoritative. During this downgrade process, the config.shard.catalog.databases collection is dropped as part of the finalizeDowngrade step in setFCV.

Because checkMetadataConsistency assumes the shards are still authoritative, it raises a MetadataInconsistency, expecting to find an entry in the shard catalog. This results in a false positive.

Example error:

{
  "type": "MissingDatabaseMetadataInShardCatalog",
  "description": "Found database metadata in the global catalog but not in the shard catalog or not in a consistent state"
}