Answer
It means the database-stored metadata for that specific projection (client, server, and API-doc metadata all get deployed together when a projection is redeployed) has changed underneath an active session or cached state, and the OData provider hasn't picked up the new version yet. If it doesn't self-resolve on the next request (the provider is meant to detect this and reload), clear the Aurena projection, metadata, and lobby caches — that reliably clears a stale-metadata state like this tied to a specific projection that was recently redeployed.