Exporting large figure on headless servers

I am trying to export some large figures (~1e4 by 1e4 surf plots) into bitmap images directly on our HPC cluster. Here is some test script I generated:

n=1e3;
[X,Y,Z] = peaks(n);

fig=figure('visible', 'off');
surf(X,Y,Z,...
    "EdgeColor","none","FaceColor","flat")

exportgraphics(fig,"Z.png",'Resolution',1200)

colorbar
caxis([0,10])
daspect([1,1,1e-2])
axis tight
title(append("$\bar{t}=",num2str(0,"%.3f"),"$"),"Interpreter","latex")
fig.CurrentAxes.FontSize=16;
fig.Position = [0,0,6,6];
fig.Units = 'inches';

exportgraphics(fig,"Zm.png",'Resolution',1200)
print(fig,"Zp.png",'-dpng','-r1200')
close(fig)

imshow(imread("Z.png"))

imshow(imread("Zm.png"))

imshow(imread("Zp.png"))

MATLAB was started with -nodisplay -nodesktop -nosplash options.

The problem is that when n is large enough (~1e4) the exporter seems to hang there forever, without any noticable consumption in CPU or RAM. Even for smaller n, the exported images are of crappy resolution, despite I specify a 1200 DPI, as you can view above. I have also attached the output generated on our HPC cluster. Is there anything I can do?