[SOLVED] Rule Engine Error ("Error while creating ScriptEngine - NullPointerException")

Hello

I tested jython some days ago and the test scripts worked. Today I wanted to develop further. However, none of the scripts is working anymore. If I try to save them I got the following error message:

22:32:29.889 [DEBUG] [ort.internal.loader.ScriptFileWatcher] - Script loaded: test02.py
22:32:30.900 [DEBUG] [ort.internal.loader.ScriptFileWatcher] - in queue: {}
22:32:30.908 [INFO ] [ort.internal.loader.ScriptFileWatcher] - Loading script 'test02.py'
22:32:30.942 [ERROR] [ript.internal.ScriptEngineManagerImpl] - Error while creating ScriptEngine
java.lang.NullPointerException: null
        at org.eclipse.smarthome.automation.module.script.internal.GenericScriptEngineFactory.scopeValues(GenericScriptEngineFactory.java:59) ~[?:?]
        at org.eclipse.smarthome.automation.module.script.internal.ScriptEngineManagerImpl.createScriptEngine(ScriptEngineManagerImpl.java:88) ~[?:?]
        at org.eclipse.smarthome.automation.module.script.rulesupport.internal.loader.ScriptFileWatcher.importFile(ScriptFileWatcher.java:164) ~[?:?]
        at org.eclipse.smarthome.automation.module.script.rulesupport.internal.loader.ScriptFileWatcher.processWatchEvent(ScriptFileWatcher.java:135) ~[?:?]
        at org.eclipse.smarthome.core.service.WatchQueueReader.lambda$3(WatchQueueReader.java:323) ~[?:?]
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [?:?]
        at java.util.concurrent.FutureTask.run(FutureTask.java:266) [?:?]
        at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180) [?:?]
        at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293) [?:?]
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [?:?]
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [?:?]
        at java.lang.Thread.run(Thread.java:748) [?:?]
22:32:31.005 [ERROR] [ript.internal.ScriptEngineManagerImpl] - could not load script as no engine is created

I rebooted the pi (with openhab 2.3.0-1) and re-installed the rule engine as well. No success.
Any thoughts?

Solution:

ps -efa | grep -i jython

I killed the process (kill -7 id) and afterwards it worked again.