Bad Request open two tabs with the same web

We have a problem (Bad Request) using Azure AD B2C, when open two tabs with the same web app, the steps to reproduce the behaviour is:

1. Open the portal URL
2. Click on Register as New User
3. Copy URL to another tab on the same browser
4. Click on Register as New User (on the second tab opened)
5. Once the registration screen opens, click on “Login”
6. Return to the first tab and click on “Login”
7. Then first tab shows error Bad Request (400)

Can help us with this problem? I look for the solution but in any post is resolved.

Start by reproducing the two-tab flow against the portal URL with Azure AD B2C: register in both tabs, then select Login in the second and first tabs. The reported completion condition is preventing the first tab from returning Bad Request (400). No source file, test, or entry point is identified, and the issue has had no recent response.

Written by the indexing model from the issue text.