I'm seeing somewhere in the WS API tests of mine an error with exception conversion of a bad app ID sent in as an argument to a GET. I know it's in ATS, but a scan of the core RM web services implies a same problem
WebServices.parseApplicationId() uses ConverterUtils.toApplicationId to convert an argument; this throws IllegalArgumentException, which is then handled somewhere by jetty as a 500 error.
In fact, it's a bad argument, which should be handled by returning a 400. This can be done by catching the raised argument and explicitly converting it