Why does x-requested-with block selectively on CORS requests?

Question

CORS

There is a page on one server that makes an ajax request to another server via ajax (jquery).

One of the users is getting an error in Chrome (it works for everyone else):

Access to XMLHttpRequest at 'api-new.example' from origin 'api.example' has been blocked by CORS policy:Request header filed x-requested-with is not allowed by Access-Control-Allow-Headers in preflight response

Allowed headers on the server where we are knocking

Access-Control-Allow-Headers - Authorization,x-app-instance-id

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Can you tell me which way to look?