Debugging a C#/Java Proj related to REST/JSON Web-Service

I have a Java project in IntelliJ (i.e. a dummy server providing test data for a REST/Json Web-service) and C# code which contains 12 test-scenarios. Both compile fine .. The Java code contains the Jersey Web-server, it uses also json, JacksonJson, Grizzly, glassfish and javax; it was built with maven. On the client (C#) site the Webservice is using RetroFit 2.0 and is using multi-threading to send/receive data. All methods (on the Java/C# side) have try/catch clauses with output to error-log files. Both interface classes (web-service) are summarized in 2 additional txt files, allowing to compare the used names and datatypes easily. Currently, the Java Algo is throwing ArrayIndexOutOfBoundsException errors. Other run-time errors may show up as well. Goal is to have all 12 test-scenarios running without errors on both sides.