UCS Kopano-Webapp Window invisible icons

Hello!

My System:
Univention UCS 4.3
WebApp: 3.4.2.1108+36.1
Kopano Core: 8.4.5.0
Z-Push: 2.3.8+0-0

If i set up an seperate browserwindow (istead of using the webapp tabs) the icons of the texteditor are not visible.

Any Idea what i can do?

0_1523952259168_kopano-webapp-icons-invisible.png

EDIT:
It is working when using the Tabs.

Thanks,
Chackl

Ticket for this issue is: https://jira.kopano.io/browse/KW-1416

Hello!
Thanks - I just noticed that we have used an old webapp - we updated it and works now - just fyi ;)
Thank you!