Interesting. After deinstalling some of the dependencies and reinstalling them I still have the same 500 response, but no error in the logs. Only two warnings:
2022-01-02 11:50:41,980 [http-nio-8080-exec-30 - http://wiki/bin/jsx/XWiki/InplaceEditing?language=en&docVersion=5.1] WARN c.x.x.w.JsxAction - Failed to send SX content: [java.io.IOException: Broken pipe]
2022-01-02 11:50:42,053 [http-nio-8080-exec-14 - http://wiki/bin/jsx/AnnotationCode/Script?language=en&docVersion=3.1] WARN c.x.x.w.JsxAction - Failed to send SX content: [java.io.IOException: Broken pipe]
UPDATE: No, after a restart of the container, the original StackTraces are back