Support request: Redirect to login on successful login when using fpm-alpine with nginx

[kuhler-Stratege]

Hello,
I am following #253 and got pma to load the login page successfully. However when I am trying to login no matter if correct or incorrect, I always get redirected back to the login page without any message etc.
I am trying to setup fpm-alpine as a second virtual host of my nginx docker container. When using the apache version of pma instead and accessing the apache server directly, everything works fine, so maybe I have some faulty nginx configuration but I have no idea anymore what it could be and could not find a solution online.
Any idea why I always get redirected back to the login page after login?

Here are my files:

• docker-compose.yml: https://pastebin.com/DDng4sL3
• default.conf: https://pastebin.com/AFmBvG1H