Panel keeps logging out every few minutes (invalid csrf token)

I’m running kirby in docker containers since a long time. But i noticed some strange behavior since 3.6.0, but i’m not sure how it could have to do with the version.

When logging in into the panel everything seems to be alright. After a few minutes the panel logs me out and i’m getting the login screen again. The csrf token is invalid. I have to reload the login page once and then i can re-login again. After a few minutes the panel logs me out again. That happens every few minutes, i i’m only able to use kirby like for 2 minutes after i have to re-login again and again.

In docker-compose.yml these 3 folders are in docker volumes, the rest of the folder are bind-mounted and directly accessible by both, the host and the container:

      - kirbycache:/var/www/html/site/cache
      - kirbysessions:/var/www/html/site/sessions
      - kirbyaccounts:/var/www/html/site/accounts

In the sessions folder there a lot of .sess files.

How can i track that down? There seems to be no additional information about why the session breaks every few minutes…

No controllers, no models, no plugins - plain kirby - that means no problem with newlines in php files.

This behavior occurs whenever you leave another tab in the browser open, just sitting on the login page. The login page periodically seems to reload, and when it reloads, the other session gets killed.
That means, i forget to close the kirby panel in another browser in the office, and when using it from home, i get logged out every 1-2 minutes because the browser from the office is killing the session.