function calling another function gives error

I am initiating a function based on a QpushButton. The function in tern calls another function. It is like a chain: button call a first function and first function calls second.

I get "Process finished with exit code -1073740791 (0xC0000409)". If I do not call call second function, everything seems fine. Any suggestion how to fix it.

    def loadIns_app(self):  
        print("Loading Waveforms")
        self.readBitCheck(self)

    def readBitCheck(self): 
        print("Read Values")