MATLAB stops reading data

So, I want to read data of a STM32F103RBT6 development board. I am able to receive the data though the STM for 1-2 minutes after which the communication abrubtly ends and I need to restart MATLAB to reset the communication link before I can rerun the script. Please help

Matlab code:

clc
clear
try
s=serial('COM4','BAUD',115200);
fclose(s);
fopen(s);
l=256;
p=zeros(1,l);
    q=ones(1,l);
    tic;
    for j=1:l

        z=fgets(s);
        string(z);
        p(1,j)=hex2dec(strtrim(z));
    end
    toc;
    plot([1:256l],p);xlim([0 l]);drawnow
    while(1)
        for i=l:-1:2
            p(1,i)=p(1,i-1);
        end
        z=fgets(s);
        string(z);
        p(1,1)=hex2dec(strtrim(z));
        plot([1:256l],p);xlim([0 l]);drawnow
    end
catch me
    fclose(s);
end
fclose(s);