plot points not visible for markersize <13

Hi, By using the plot function in Matlab 2015b, suddenly the dots became almost invisible on the figure on screen. Their size do not change at all by adjusting the markesize, but suddenly appear only at markersize 13 or more. Other markers are visible and their size change as it should by setting the markersize. Also, printing the figure instead of displaying it, works as usual. Any idea what the issue is, please? Would it be a default parameter that had changed and that I should put back?

[Walter Roberson]

This just might be related to https://www.mathworks.com/matlabcentral/answers/359509-problems-with-the-function-plot