Unable to validate the information provided (No custom policy)

Question

I have created the default triplet of userflows (B2C_1_editprofile1, B2C_1_resetpassword1, B2C_1_signin1) and have no custom policy. I followed this guide https://learn.microsoft.com/en-us/azure/active-directory-b2c/force-password-reset?pivots=b2c-user-flow

But when testing the user-flow (after providing a new updated password) I only get the error message "Unable to validate the information provided" with no futher information, no console error and no failed network fetches.

Question 1. How do I get this to work?
Question 2. How can microsoft consider it ok to have non working tutorials, or even consider this product ready for usage by general customers, when such basic functionality is not working by default!