Docker: Roundcube hangs on login

[kishon]

I have two docker containers: docker-mailserver and roundcube. Everything was configured and is working properly. Nginx on host is a proxy to roundcube in docker container.
But after some time that the containers are working in some moment there is login problem with roundcube.
Login page loads as always very fast but after providing saved in browser credentials and clicking Login the login process hangs and says only "Loading...". After a few whiles I get timeout.

Seen this problem on the Internet but no proper solution was provided.

Any help?