Manually installed certificates are marked as invalid

Just solved the certificate issue with the following post: System Diagnostics - Check Validity Of SSL Certificate

I needed to install the root-certificate.

Although the changes from the active directory are still not showing up in UCS. The connector log shows the following error repeatedly:

try to sync 45 changes from UCS
done: Tue Apr 14 10:09:29 2020
 --- connect failed, failure was: ---
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/univention/connector/ad/main.py", line 302, in main
    connect()
  File "/usr/lib/python2.7/dist-packages/univention/connector/ad/main.py", line 204, in connect
    ad.initialize_ucs()
  File "/usr/lib/python2.7/dist-packages/univention/connector/__init__.py", line 877, in initialize_ucs
    self.poll_ucs()
  File "/usr/lib/python2.7/dist-packages/univention/connector/__init__.py", line 964, in poll_ucs
    self._generate_dn_list_from(files)
  File "/usr/lib/python2.7/dist-packages/univention/connector/__init__.py", line 939, in _generate_dn_list_from
    dn, new, old, old_dn = cPickle.load(f)
EOFError

 ---     retry in 30 seconds      ---