/usr/share/univention-lib/join.sh missing

Hello community,

I tried to update to UCS 5.0 recently, and my webinterface doesn’t work now.
The server I am doing this on is a testing VM, cloned from our main UCS server.
The main server doesn’t have the file either, but runs smoothly for some reason.

I noticed the error when I wanted to open the web interface, it didn’t work and I decided to reinstall the administration packages:

# apt install univention-management-console-frontend univention-management-console

[...]
/var/lib/dpkg/info/univention-management-console-module-ipchange.postinst: 6: .: Can't open /usr/share/univention-lib/join.sh
[...]
/var/lib/dpkg/info/univention-management-console-module-ucr.postinst: 6: .: Can't open /usr/share/univention-lib/join.sh
[...]
Errors occured while updating:
 univention-management-console-module-ipchange
 univention-management-console-module-ucr
E: Sub-process /usr/bin/dpkg returned an error code (1)

Any hints or help appreciated.