Invalid setting of assignin() when used in App Designer

I start an mlapp-file (app designer) with an m-file. Also i assign three variables in the base workspace before.

%m-file

assignin('base', 'process_time', '0'); 
assignin('base', 'start_process', '0'); 
assignin('base', 'force_stop', '0'); 
new_app = gia_app;

The app has two buttons who are supposed to change the value of two of the variables i assigned before.

          %-mlapp-file

          % Button pushed function: start_btn
          function start_btnPushed(app, event)
              assignin('base', 'start_process', '1'),
              set(app.start_btn, 'Enable', 'off');
          end

          % Button pushed function: stop_btn
          function stop_btnButtonPushed(app, event)
              assignin('base', 'force_stop', '1');
          end

When i run the m-file, I get the error-message:

    Error using gia_exe (line 12)
    Invalid setting in 'gia_sim/Notstopp' for parameter 'Value'.    Error using gia_exe (line 12)
    Invalid setting in 'gia_sim/Start button' for parameter 'Value'.

Even weirder, when i start the mlapp-file (app) without the m-file, I don't get the error-message and everything works as intended. Any ideas?

[Philipp Küsters]

Apparently u have to not use the ' ' when assigning a number. Correct would be:

assignin('base', 'start_process', 1),