Hi @urbanisierung ,
Thank you for raising this topic on Auth0 Community!
I tested this issue on my end and could not repeat the same.
If you have customized your New ULP branding page template with Management API , could you please share the details of the template?
Maybe it worth trying to use the default template. To do so, use the delete endpoint.
curl --request DELETE \
--url 'https://YOUR_DOMAIN/api/v2/branding/templates/universal-login' \
--header 'authorization: Bearer MGMT_API_ACCESS_TOKEN'
Please keep us updated on how it goes. Thanks!