[IMPORTANT] As of version 4.1 Comments are now a separate Source (if you are using Comments for any Post Type Source you will need to edit your Engine and rebuild your index, this is not done automatically and should be planned for when updating)
[Improvement] Indexer handling of concurrent invocations, health check/restart when process encounters Errors
[Improvement] Indexer in multisite environment
[Fix] AND logic restrictions in some cases