Upon receiving a request to reindex, Upgrade Assistant (UA) stores the requester's credentials in memory and uses those credentials when updating saved objects and issuing requests for other reindexing related operations.

In a token-based authentication mechanism these tokens have an expiration time that could expire before reindexing work completes causing the task to stall. With state of reindexing tracked inside of saved objects this should be recoverable but the ideal would be that no recovery is required.

At the moment there is no simple way to refresh the auth token on behalf of the requester.

See https://github.com/elastic/kibana-team/issues/1331 for a similar issue and a proposed solution.