'Error using axes' when i use another function in a GUI

Hello, i made a GUI that with axes1, a togglebutton and lots of input variables. the problem is, that the plot does not appear in axes1. instead, a new figure appears. i tried axes(handles.axes1) but then, this error appears:

Error using axes Invalid axes handle

Error in BalkenbiegungGUI>togglebutton1_Callback (line 266) axes(handles.axes1);

Error in gui_mainfcn (line 95) feval(varargin{:});

Error in BalkenbiegungGUI (line 42) gui_mainfcn(gui_State, varargin{:});

Error in matlab.graphics.internal.figfile.FigFile/read>@(hObject,eventdata)BalkenbiegungGUI('togglebutton1_Callback',hObject,eventdata,guidata(hObject)) 266 axes(handles.axes1);

I tried a little test GUI without calling other functions inside it. It works then. Does anyone have an idea how to fix this? Thank you, Peter