Please see this posting at Stack Overflow: http://stackoverflow.com/questions/42446688/baffling-logback-bug-timebasedarchiveremoverarhiveremoverrunnable

... the NoClassDefFoundError occurred at line 231 of ch.qos.logback.core.rolling.helper.TimeBasedArchiveRemover, method cleanAsynchronously

I have no idea what's going on because the class said to be "non-existent" is present in that self same .java file...