I figured it out by myself.
The Problem was on my Openhab 3 System. There was a misconfiguration with Python and PIP.
Some modules like ‘request’ and ‘JSON’ were not correctely installed by PIP.
After a reconfiguration from Python and PIP , some Parts from the svg_combiner worked correctely, but the output failed.
I found a newer version of the svg_combiner script in the Forum and with some modification it worked like a charm.
Everything is fine now.