Cannot use Win10 Hello PIN (looping dialog)

I run Windows 10 Pro, nothing special about the set up. Been using the PIN system for about a year or so when suddenly I got an issue. Anytime I access the store or xbox apps, it would request the PIN. Here I would get stuck in a loop. Specifics on the loop are below.

I tried resetting group policies, security settings, and resetting windows itself to no avail.

After deleting the NGC folder (C:\Windows\ServiceProfiles\LocalService\AppData\Local\Microsoft) I was able to access the Store, this time it requested my standard MS/Win password. No looping.

When i try to set up the PIN again, I get the loop. I then tried reinstalling windows and again I get the loop when I attempt to set up the PIN.

Any ideas how I can get round this? I can use my password for now, but I would like to use the Hello PIN if possible.

The Loop:

The loop itself occurs when I get this screen:

Selecting ANY option, whether it is entering a PIN, clicking OK / Cancel, or closing the dialog itself, will result in a second delay then the same dialog opens up again. When I already had a pin set up, it just asked for input (instead of setting up a new pin). It didnt matter if I typed the pin in correctly or not, the box would disappear and then immediately re-appear.

The only way to get out the loop is to close the process in the taskbar.

EDIT: In Addition, when i try to switch to a local account I get this error, perhaps indicating the problem is with account settings on my PC somewhere?

Another edit: I tried MS Help and the only thing they could come up was to create a new user account (which worked). I would rather keep my old one so I do not have to reinstall all my tools and get authentication token etc.

I did find this report in event logs whenever I try to set the PIN:

Faulting application name: CredentialUIBroker.exe, version: 10.0.18362.1, time stamp: 0x38c5a224
Faulting module name: ntdll.dll, version: 10.0.18362.418, time stamp: 0x99ca0526
Exception code: 0xc0000374
Fault offset: 0x00000000000f9269
Faulting process ID: 0x5d44
Faulting application start time: 0x01d58bc991337e8b
Faulting application path: C:\Windows\System32\CredentialUIBroker.exe
Faulting module path: C:\WINDOWS\SYSTEM32\ntdll.dll
Report ID: a47fe8b6-ade4-4d7f-a146-f106642940bb
Faulting package full name: 
Faulting package-relative application ID: 

I cannot guarantee this will work for everyone, it may be just dumb luck, but this is how I stumbled upon a solution.

As I mentioned in the Q I removed the NGC folder content, I then created a new account (local) and verified PIN was working. Then I added an MS account to it (essentially replicating my problem account). Again I verified the PIN etc was working.

At this point you could just switch to the new account, but that wasn't acceptable to me so I did a lot of "faffing about". I discovered that if I deleted the new account completely and switched back to the old one, the new NGC folder remained. Sadly, so did the problem.

I went to the Credential Manager (Control Panel\All Control Panel Items\Credential Manager) and removed a few older tokens (sorry can't remember them all), but made sure to remove my MicrosoftAccount and Skype tokens, basically anything that smelt Microsofty. Then I deleted the new NGC folder content and rebooted.

Suddenly it just worked again. I tried to remove my account and go local and that seems to work too. So I assume the NGC might not have helped and it was just a corrupt credential?

Any any rate, I have put everything in I could remember in case it helps a fellow browser someday. If someone out there can tell me why this would work, when I tried all the steps before individually, then please relieve me of my ignorance!