That is the normal behaviour for the last few releases.
One way to straighten the tick labels without having them overlap is to reduce the font size —
x = 0:20:160;
y = rand(size(x))*100;
figure
plot(x, y)
Ax = gca;
set(Ax,'XTick',x, 'XTickLabel',x);
Ax.XAxis.FontSize = 16;
xlim([min(x) max(x)])
figure
plot(x, y)
Ax = gca;
Ax = gca;
set(Ax,'XTick',x, 'XTickLabel',x);
Ax.XAxis.FontSize = 10;
Experiment to get the desired result.
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