Zigbee2MQTT light groups not showing brightness for the group

Yesterday I finally figured out how I could make a group in Zigbee2MQTT and then binding a button for it.
Happy enough, Home Assistant found my group instantly and I added it to my dashboard.

Today I found out, that I can turn on and off, change brightness etc., but whenever I close the popup and open it again, the brightness is reset to 0.

I can’t in any way figure out why Home Assistant sees it as 0. In the MQTT broker, it tells the correct brightness for the group, so the info does exist.

What am I doing wrong?

Did you figure out the issue? I have multiple groups created, and so far only 1 has this issue