Vertical white line artefacts on exported figures [R2017a]

I'm trying to export figures to vector format files (eps, pdf, svg) from matlab, and the rendering is pretty bad. I found that when using dashed or dotted lines, eps and pdf format gives a very bad rendering where svg gives the right one.

However, when I try to export a figure from contourf/imagesc/surf, I have white lines that appears only on the exported figures. (Matlab rendering is ok).

How do I fix that ? I tried to change the rendering with

set(gcf,'renderer','painters')

from this topic https://fr.mathworks.com/matlabcentral/answers/99614-why-do-i-get-white-line-artifacts-in-my-image-when-rotating-a-3-d-surf-plot-in-matlab-7-1-r14sp3p3 , but the print/saveas command keep matlab busy for hours, so I have to close everything manually.

here is the code used to print this figure :

figure
[C2,h2] = contourf(X',Y',Z2,50) ;
h2.LineStyle = 'none' ;
colormap(gray)
hold on
plot(k(Indmax),alpha,'k-','Linewidth',2)
hold on
plot(k(Indsep),alpha,'k--','Linewidth',2)
ax = gca ;
set(gca,'FontSize',14)
c = colorbar ;
c.Label.String = '$\sigma$' ;
c.Label.Interpreter = 'latex' ;
c.FontSize = 14;
c.Label.FontSize = 18 ;
c.Location = 'northoutside' ;
ylabel('\alpha (°)','FontSize', 18)
xlabel('$k$','Interpreter','latex', 'FontSize',18)
yticks([-90 -45 0 45 90])
set(h2,'edgecolor','none')
% shading(gca,'flat')
% set(gcf,'renderer','painters')
saveas(gca,'Sigma_3D_r1.6','svg')
% print('-dsvg','-painters', 'Sigma_3D_r1.6')