Very bad quality of output, not smooth lines

[quark67]

I take the bottom image in page 4 of the documentation:

When zoomed, this is what we saw. On left:

On right:

Is there a way to obtain a smoothed red curve instead of these little pieces of straight lines?

On page 5 of the documentation, we have:

With the same ugly output:

But not always:

so there is a bug with the "photon" or "charged scalar" lines, but not with the "gluon" line.