Hi there, long time user, first time poster.
I was just trying to login to my account on Gitlab.com via Github, and I encountered a 422 page. I’ve cleared cookies and tried different SSO providers, and they all are resulting in a 422.
Specifically it looks like the POST to https://gitlab.com/users/auth/<auth_provider> is what is returning a 422. In the network tab in Firefox I see 422 responses from POSTs to https://gitlab.com/users/auth/github, https://gitlab.com/users/auth/salesforce, etc…