Use TCPIP with callback inside a class

I have a problem with a the tcpipsocket in use with a class as property. The class inherits handle to work with constructor and destructor. All works fine until I activate the BytesAvailableFunction. After the Activation the destructor will no longer be called by deleting my workspace. It seems that my class is referenced somewhere in the instrument control, because calling instrreset after deleting my workspace, calls my destructor function.

Here is a minimal example that reproduce the error:

classdef wsg50_mini2 < handle

    properties
        TCPIP
    end

    %PUBLIC METHODS
    methods

        %CONSTRUCTOR
        function obj = wsg50_mini2(varargin)
            fprintf('################# I am created #################\n')

            obj.TCPIP = tcpip('localhost',1000);
            obj.TCPIP.OutputBufferSize = 3000;
            obj.TCPIP.InputBufferSize = 3000;
            obj.TCPIP.ByteOrder = 'littleEndian';
            obj.TCPIP.Timeout = 1;

            %Setting up Callbackfunction
            obj.TCPIP.BytesAvailableFcnMode = 'byte';
            obj.TCPIP.BytesAvailableFcnCount = 1;
            obj.TCPIP.BytesAvailableFcn = {@obj.TCP_Callback, obj};
        end
    end

    %PRIVATE METHODS
    methods (Access = private)

        %DESTRUCTOR
        function delete(obj)
            fprintf('################# Hey I am called! #################\n')
            instrreset
        end
    end