I took me a very long time to understand that my problems arise from a version mismatch of slf4j-api and logback. Even after realizing the connection to my problem I found no documentation which versions match, i.e. which one to test with. I needed to just try it out, that's discusting. Even now, after I realized that the latest version has a serious bug I again need to try to find the matching version of the logback release before...