New Windows 10 user is logged out immediately after login

Explanation:

What's the problem?

Your problem is caused by a corrupted NTUSER.DAT file.
Windows creates one user profile folder in C:\Users\ for each user account, excluding special accounts like SYSTEM, and each one of these folders contains a NTUSER.DAT file, which is used to store settings and such things.

Why are only new accounts affected?

Well that's because there's one profile folder called Default which is not associated with any profile instead it gets copied each time a new profile folder is needed to fill that new profile with all necessary files.So every modification/damage of the Default profile will be copied into all new profile folders.

So finally your problem is a corrupted NTUSER.DAT file inside the Default profile folder.

How to fix it?

The only way I know is replacing NTUSER.DAT in the Default profile folder with a fresh one of a new Windows 10 installation or replacing it with a backup. For the first option you will lose some system-wide shortcuts for a program in a new account on the desktop, some system-wide user-specific settings, etc., but it won't affect existing profiles.
Maybe somebody has a better idea.