Error: Cannot read 'data' of undefined

[Archehandoro]

Hello,

Some time ago, I installed successfully the docker version of mailman and all was working fine. However, after some time without using it, I was trying to log in to the web UI getting the title's error "Error: Cannot read 'data' of undefined"

Performing docker logs on the container only returns "Mailman is running on http://127.0.0.1:4000/ in production mode", so I am a bit puzzled.

The only change I have performed on the server, unless my memory fails me, is that I have changed the postfix compatibility mode to 2, that effectively disables it. Reverting the change does not remove the error nor allows me to log in again.

Any ideas? Thanks!