I have implemented Forms based authentication and Windows authentication after reading soultion on google and found step by step solution in https://www.codeproject.com/Tips/991205/Branding-Default-Login-Page-for-Form-Based-Authent
Everything is working fine when external user login and click "SignOut" it come back to same Custom Login Page.
But when windows user logins and then click "SignOut" then Error appears
"Something went wrong...".
as mentioned I also set
Set-SPCustomLayoutsPage -identity "Signout" -RelativePath /_layouts/Sp.Login.Custom/Login.aspx" -WebApplication "your web application url"
but still having same issue