Need new Oculus/Meta nonce for authoring when switching runners?

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I'm using the Oculus custom authentications for Fusion and am having a few issues:

On first connection to a shared runner, it connects fine, but OnCustomAuthenticationResponse() never gets called.

When I disconnect from that runner and try to connect to a new one, I get a failure message "AuthenticationFailedException: Oculus nonce validation failed". I think this is because the nonce might be getting invalidated once it's used. BUT I'm pretty sure there is now a valid token from the previous successful auth, so why isn't Fusion using this to re-auth, or how do I get it to do so? The only other alternative seems to be to regenerate the nonce every time I want to log in to a runner or service (I'd have to do this if Voice used Oculus auth too).