Keyboard inactive / does not respond during script in MATLAB R2018b running on Ubuntu 18.04

Hi,

I'm running a script for an experiment using a function (from a different, experiment controller, ExpControl.m file), which waits for a 'space' to continue or a 'q' to quit (script is here below). However, Matlab does not respond, as if the keyboard were not functioning. If I use the mouse, I can click into the command window, where I can type, but it is not recognized as a command (screenshots below). At this point I can quit with ctrl + c, but I have no idea what could be reason for it. The script worked perfectly well on a MacBook Pro OSX 10.11. I've just moved to Linux Ubuntu 18.04.2 LTS, running on a Dell G3 with Nvidia GeForce GTX 1050 Ti. Do you have any suggestions?

Thank you!

%Script from the script of the specifi experiment
if ExpControl_ELTE('WaitSpace')
    %the experimenter QUIT
    stopexp=1;
    %FINISHING UP
    PsychPortAudio('Close');
    ExpControl_ELTE('FinishExp');
    break
end


%Experiment controller file
function state=ExpControl_ELTE(command,varargin)
    
    state=false;
    switch lower(command)
        case 'iskey'
            % Checks whether a given key is pressed
            if nargin<2
                key=0;
            else
                key=varargin{1};
            end
            state=IsKey(key);
            return
        case 'waitspace'
            % Waits for Space or Q
            state=WaitSpace();
            return
       
        otherwise
            error('Invalid command. Call "help ExpControl" to find out the available commands.');
            return;
    end
return

function ctrl=IsKey(key)
    global KEYBOARD;
    [keyIsDown,secs,keyCode]=PsychHID('KbCheck', KEYBOARD);
    if ~isnumeric(key)
        kc = KbName(key);
    else
        kc = key;
    end
    ctrl=keyCode(kc);
return

function state=WaitSpace()
    QKEY=KbName('q');
    SPACEKEY=KbName('space');
    while 1
        if IsKey(QKEY)
            state=true;
%            while IsKey(QKEY)
%            end
            return;
        end
        if IsKey(SPACEKEY)
            state=false;
            return;
        end
    end
return