_bulk_docs is a write operation, not a read operation, so I don’t think the error above is relevant to the ‘device doesn’t reflect the changes’ issue.
A common issue when Couchbase Lite can write but not read documents is the security access of the Couchbase Lite user. I’d suggest verifying that they have read access to the document you’re writing to the server - the https://docs.couchbase.com/sync-gateway/current/learn/read-access.html documentation might be helpful here.