v.20.4Bug Fix
Prefer fallback_to_stale_replicas over skip_unavailable_shards to avoid query failures
Preferfallback_to_stale_replicasoverskip_unavailable_shards, otherwise when both settings specified and there are no up-to-date replicas the query will fail (patch from @alex-zaitsev ) #10422 (Azat Khuzhin)