I realize this is an old thread but rather than starting a new one for the exact same issue I want to use this to show some history, it is 2023 now and we are on version 9.0.0 on a Windows platform and are still getting this same exact error I have opened a technical support case with Splunk and hope to provide you with updates, troubleshooting tips and hopefully a proper solution for this issue  Note: in my case I found the "missing" buckets on the Index Cluster Master UI under Settings \ Index clustering \  Bucket Status \ Fix Up Tasks section     ... View more