Where is your problem: In the admin panel
The essence of the problem: At what point did it kick you out of the admin panel. First, go and make a redirect to the authorization form. When receiving authorization with the specified data, the session should be recorded, but redirected. When deleting the cache and cookies, the problem remains. According to the logs, there are no errors, no response 200.
How to reproduce the problem: It is not known exactly. But the fact is that this problem exists.