I have a login problem in the Wordpress Admin panel.

First I have the redirect loop wp-admin to wp-login with the param reauth=1.

I tried all the suggestions found in the support forums but none of them worked for me (clear browser cookies, delete plugins, themes, htaccess file, define siteurl in wp-config ...). The site was moved to https can that cause the issue ?

Second I have some kind of a session problem ? when I go to a page from a completely different browser in a different device, I find myself logged in with the last login I was trying to use in the first browser? it's like it keeps the last login in memory, this is a security problem because any user can be logged it to the admin panel...

I have never experienced this problem before, does anyone have an idea how to solve this ?