Java exception, serialization, MATLAB, WEKA, CHIRP

I'm using MATLAB-WEKA interface to run some classifiers. But when I use CHIRP classifier and save/load classifier object and try to use itI'm getting Java exception. There is no problem with using this object directly from the memory without saving. There is also no problem for saving/loading and using classifier object from other algorithms like e.g. Spegasos.

According to MATLAB doc object to be saved/load must implement Serializable https://www.mathworks.com/help/matlab/matlab_external/creating-and-using-java-objects.html#f46890

but according to doc from CHIRP it is done already so perhaps some part of implementation is missing or is a MATLAB problem. MATLAB saves\loads this object and don't complain. So my question is how to troubleshoot such problem i.e. how to find out what is missing and where the fault lies.

here is a CHIRP package https://www.cs.uic.edu/~tdang/file/CHIRP1.0.1.zip

Krzysztof

    Java exception occurred: 
    java.lang.NullPointerException

    at weka.classifiers.misc.chirp.Trainer.tranformTesting(Trainer.java:347)

    at weka.classifiers.misc.chirp.Classifier.classifyInstance(Classifier.java:62)

    at weka.classifiers.misc.CHIRP.classifyInstance(CHIRP.java:256)

    at com.mathworks.jmi.NativeMatlab.SendMatlabMessage(Native Method)

    at com.mathworks.jmi.NativeMatlab.sendMatlabMessage(NativeMatlab.java:266)

    at com.mathworks.jmi.MatlabLooper.sendMatlabMessage(MatlabLooper.java:120)

    at com.mathworks.jmi.Matlab.mtFevalConsoleOutput(Matlab.java:1778)

    at com.mathworks.jmi.MatlabMCR.mtFevalConsoleOutput(MatlabMCR.java:1232)

    at com.mathworks.timer.MWCallback$callbackEvent.run(MWCallback.java:502)

    at com.mathworks.jmi.NativeMatlab.dispatchMTRequests(NativeMatlab.java:458)