Under some unclear circumstances the ScriptEngine in PipeBindings does not get initialized.
There is a solution out there to attach Nashorn to the system bundle. Appart from that I was able to fix it by using a different constructor: ScriptEngineManager(null).
The issue can be reproduced by deploying https://github.com/bcsott/migration-tool
When it fails the following is written to stderror.log:
ScriptEngineManager providers.next(): javax.script.ScriptEngineFactory:
Provider jdk.nashorn.api.scripting.NashornScriptEngineFactory not found