right way to upgrade from v4.0.7?

[sciBernd]

Hello, beginner needs a hint how to upgrade netbox.
I followed 'First time Setup', set VERSION to v4.0.7-2.9.1, integrated our existing data (restore postgres, netbox volume: netbox2-data:/opt/netbox/netbox) started using docker compose, everything looks fine.

Now I want to upgrade to netbox v4.1:
docker compose down, set VERSION to 4.1, docker compose pull, docker compose up -d
Everything looks fine, logs are ok.
Netbox-container uses netboxcommunity/netbox:v4.1.

But netbox version stays on 4.0.7 (lower right corner of website & info in Admin -> System).
What should be done? I didn't found hints regarding this, tried upgrading to other versions, my netbox remains on 4.0.7 all the time.

Thanks in advance for a little light on my missunderstanding.