@vrademacher ah, great, that wasn't clear to me!
Then while the forum and community support might be able to help, I'd recommend filing a support ticket by logging into account.fusionauth.io and going to the support tab.
Feel free to reference this forum post if you'd like.
If you'd like to continue to debug this issue here, can you please give me a bit more info?
It'd be great to know:
the version of fusionauth where you are encountering the issue the login flow (login api, oauth authorization code grant, etc) the browser the customer is using anything unique about the customer as opposed to other customers that are not having this issue