Hi @groupion-it ,
no this is still not fixed by Univention. I`m not sure if they saw this already?
What I have done as workaround:
Read the LDAP phone entry for each user and modify the entry in OX database with /opt/open-xchange/sbin/changeuser with the --telephone_business1 option.
Please check follwing topic: OX Appsuite 7.10-6-ucs4 installation/upgrade - #2 by getcom
Here I found something similar in the log files which could be a hint for the developers.