@Exact_Value correct, hot_join_party_hub_failed / Error Code: 4001 are the same error. Not renamed, but it can display in either format.
I can appreciate the frustration, really. I have equal dislike for these connectivity errors 
This specific error is still under investigation, but hasn’t been fixed just yet. It will, and we’re working to resolve it as soon as possible.
I can only offer our sincerest apologies for the inconvenience during this time.