Starting Apache as service quits with SIGWINCH

When running service apache start I see in the log file this entry:

and the service apache does not start? I can find in internet what SIGWINCH means [Window size change] but it does not really help me in this case.

The file /etc/systemd/system/apache.service:

Running on SLES 12 SP1. I have compiled Apache on my own. Starting it with apachectl -k start works perfectly and I can access and run the PHP code.

My question:
What am I doing wrong that the apache service does not start. I have enabled it with systemctl enable apache. This was the output: