There is no error message, The Vault Store properties shows as Multiple like in the screenshot below. Also, The Vault Store is indexed by multiple index servers is displayed.

It has also been observed that the Multiple status might change automatically, showing instead a remote Enterprise Vault Indexing server.
The aforementioned is expected in an EV Site composed by multiple servers where not all them have a local Indexing service. This is what happens more in detail:
1. Each Vault Store is associated with one indexer (Indexing Service), and each indexer is associated with one Enterprise Vault Server.
2. If there are some Enterprise Vault servers with local Storage but without local Indexing Service, the Vault Stores that are associated with these Enterprise Vault servers are not allocated with any Indexing Service.
3. Newly archived items for those Enterprise Vault archives belonging to Vault Store without local Indexing Service cannot be indexed locally. Therefore, a remote Indexing Service with an open Indexing location will be used for Indexing.
4. Whichever Indexing Service has an open Indexing location will be used for Indexing and the Indexer in the Admin Console is assigned with Enterprise Vault server name whose Indexing Service is used for Indexing.
5. Due to the change in Indexing Service for Vault Store, multiple Indexing services get assigned to the Vault Store.