Hi @masaki @sagun786 and @filip.debacker!
Thanks for reaching out! Let’s see what we can do 
Would you mind all sending me your tenant name in a DM as well as a .har file for me to look into this further? More details on that here:
Just so I have some clarity on this, are you seeing these errors on all logins or are they specific only to Social Logins (Facebook/Google etc.)? Also is this issue only when you deploy your app or is it reproducible locally as well?
@masaki what were the differences that you noticed? The token_endpoint_auth_method should be set to none for a SPA, this would be worth confirming as that could cause an Unauthorized error.
Best Regards,
Colin