Apache 2 configtest failed: File name too long - apache2

Question

I run an apache2 webserver locally on a raspberry-pi with raspbian distro.
It worked without a problem until suddenly it can't be started anymore with
sudo /etc/init.d/apache2 start, which yields the following error:
[....] Starting apache2 (via systemctl): apache2.serviceJob for
apache2.service failed. See 'systemctl status apache2.service' and
'journalctl -xn' for details. failed!
Removing and reinstalling with apt-get doesn't solve it.systemctl status shows the following entries:
> Apr 22 11:27:16 raspberrypi apache2[18234]: [344B blob data] Apr 22
> 11:27:16 raspberrypi apache2[18234]: [293B blob data] Apr 22 11:27:16
> raspberrypi apache2[18234]: [293B blob data] Apr 22 11:27:16
> raspberrypi apache2[18234]: [293B blob data] Apr 22 11:27:16
> raspberrypi apache2[18234]: [293B blob data] Apr 22 11:27:16
> raspberrypi apache2[18234]: Action 'configtest' failed. Apr 22
> 11:27:16 raspberrypi apache2[18234]: The Apache error log may have
> more information. Apr 22 11:27:16 raspberrypi systemd[1]:
> apache2.service: control process exited, code=exited status=1 Apr 22
> 11:27:16 raspberrypi systemd[1]: Failed to start LSB: Apache2 web
> server. Apr 22 11:27:16 raspberrypi systemd[1]: Unit apache2.service
> entered failed state.
journalctl -xn yields:
> -- Logs begin at Sun 2017-04-23 07:06:12 UTC, end at Sun 2017-04-23 12:38:48 UTC. -- Apr 23 12:38:30 raspberrypi apache2[3292]: [2.0K blob
> data] Apr 23 12:38:30 raspberrypi apache2[3292]: [1.7K blob data] Apr
> 23 12:38:30 raspberrypi apache2[3292]: Action 'configtest' failed. Apr
> 23 12:38:30 raspberrypi apache2[3292]: The Apache error log may have
> more information. Apr 23 12:38:31 raspberrypi systemd[1]:
> apache2.service: control process exited, code=exited status=1 Apr 23
> 12:38:31 raspberrypi systemd[1]: Failed to start LSB: Apache2 web
> server.
> -- Subject: Unit apache2.service has failed
> -- Defined-By: systemd
> -- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
> --
> -- Unit apache2.service has failed.
> --
> -- The result is failed. Apr 23 12:38:31 raspberrypi systemd[1]: Unit apache2.service entered failed state. Apr 23 12:38:31 raspberrypi
> sudo[3278]: pam_unix(sudo:session): session closed for user root Apr
> 23 12:38:48 raspberrypi sudo[3345]: pi : TTY=pts/0 ;
> PWD=/etc/apache2/conf-enabled ; USER=root ; COMMAND=/bin/journalctl
> -xn Apr 23 12:38:48 raspberrypi sudo[3345]: pam_unix(sudo:session): session opened for user root by pi(uid=0)
Unfortunately the apache error.log contains no useful information whatsoever. But if i run apache2 configtest I get a "File name too long" error.
Strangely even after formatting my sdcard and putting a fresh copy of the distribution image on it and reinstalling apache2 the error remains.
What can I do?