Please find attached, the demo with dummy data. As I mentioned, it was working fine until May 1st. 
Also, As I mentioned, in case I call MasterApp at the end of add function data appears correctly. This means a malfunction occurred after Windows Update, and it relates to mainloop

    class MasterApp(object):
        def __init__(self, root):
        ....

        def fun_astinfo_add(self):
	    ...
	    assetinfo_lst.append(lst_values)
	    ...
	    MasterApp(root)

        ...
    if __name__ == "__main__":
        root = Tk()
        App = MasterApp(root)
        root.mainloop()