Now although appFabric needed upgrading, and to be fair, its now a skillset I’ve acquired, its not the cause. That I still havent sorted yet! But I have discovered why there’s multiple calls and 401 errors.
As this link states, its due to NTLM, something we have running. First call is an anonymous call and really a 401 error is expected. Next call is a NTML call as the first one says do that next and expects a 401 first as its a challenge request, then you should get a 200 code. All expected behaviour apparently.
So the issue I started with persists but I now know why a double 401 error happens and also how to update appFabric the correct and safe way. Even if I did have an issue halve way through, a solution was found below in order to correct and restart it.