Strange artifacts with pstricks plot

Consider the following MWE:

\documentclass[border=5pt,pstricks]{standalone}
\usepackage{pstricks,pst-plot,pst-math}
\listfiles

\begin{document}

\psset{xunit=1.05cm,yunit=1.05cm}
\begin{pspicture*}(-1.38,-2.28)(4.19,4.45)
\psgrid[subgriddiv=0,gridlabels=0,gridcolor=lightgray](0,0)(-1.38,-2.28)(4.19,4.45)
\psset{xunit=0.21cm,yunit=0.21cm,algebraic=true,dotstyle=o,dotsize=3pt
0,linewidth=0.8pt,arrowsize=3pt 2,arrowinset=0.25}
\psaxes[labelFontSize=\scriptstyle,xAxis=true,yAxis=true,Dx=5,Dy=5,ticksize=-2pt
0,subticks=2]{->}(0,0)(-6.92,-11.39)(20.96,22.23)[x,140] [y,-40]
\psplot[plotpoints=200]{-6.91776797358592}{-1.4000001}{(x^3-3*x^2-6*x+8)/(x^2-3.6*x-7)}
\psplot[plotpoints=200]{-1.399999}{4.99999}{(x^3-3*x^2-6*x+8)/(x^2-3.6*x-7)}
\psplot[plotpoints=200]{5.00001}{22.5}{(x^3-3*x^2-6*x+8)/(x^2-3.6*x-7)}
\psline[linestyle=dashed,dash=2pt 2pt](-1.4,-11.39)(-1.4,22.23)
\psline[linestyle=dashed,dash=2pt 2pt](5,-11.39)(5,22.23)
\end{pspicture*}

\psset{xunit=0.5cm,yunit=0.5cm}
\begin{pspicture*}(-7.87,-8.58)(10.82,6.44)
\psgrid[subgriddiv=0,gridlabels=0,gridcolor=lightgray](0,0)(-7.87,-8.58)(10.82,6.44)
\psset{xunit=0.5cm,yunit=0.5cm,algebraic=true,dotstyle=o,dotsize=3pt
0,linewidth=0.8pt,arrowsize=3pt 2,arrowinset=0.25}
\psaxes[labelFontSize=\scriptstyle,xAxis=true,yAxis=true,Dx=1,Dy=1,ticksize=-2pt
0,subticks=2]{->}(0,0)(-7.87,-8.58)(10.82,6.44)[x,140] [y,-40]
\psplot[plotpoints=200]{-7.75}{-4.73}{TAN(x)}
\psplot[plotpoints=200]{-4.7}{-1.58}{TAN(x)}
\psplot[plotpoints=200]{-1.56}{1.56}{TAN(x)}
\psplot[plotpoints=200]{1.58}{4.70}{TAN(x)}
\psplot[plotpoints=200]{4.72}{7.84}{TAN(x)}
\psplot[plotpoints=200]{7.86}{11}{TAN(x)}
\psline[linestyle=dashed,dash=2pt 2pt](1.57,-8.58)(1.57,6.44)
\psline[linestyle=dashed,dash=2pt 2pt](4.71,-8.58)(4.71,6.44)
\psline[linestyle=dashed,dash=2pt 2pt](7.85,-8.58)(7.85,6.44)
\psline[linestyle=dashed,dash=2pt 2pt](-1.57,-8.58)(-1.57,6.44)
\psline[linestyle=dashed,dash=2pt 2pt](-4.71,-8.58)(-4.71,6.44)
\end{pspicture*}

\end{document}


When printing this document from Adobe Reader 11.0.12 on a Windows 7 machine, artifacts as in the picture below appear:

However, they do not show up in the viewer. I do not get them when printing from OS X's Preview.app or from Foxit Reader on a Windows 8.1 machine. The issue does not seem linked to the print driver, as it happens with different printers.

The problem originally appeared in a document created by a friend of mine, I just took it over. She uses MikTeX 2.9 (and some not really up-to-date versions of PS Tricks), I tried it with TeX Live 2014 on a Mac and TeX Live 2015 on Windows 8.1. My package versions are

pstricks.sty    2013/12/12 v0.60 LaTeX wrapper for PSTricks' (RN,HV)
pstricks.tex    2014/10/25 v2.60 PSTricks' (tvz,hv)
pst-xkey.tex    2005/11/25 v1.6 PSTricks specialization of xkeyval (HA)
pst-fp.tex    2014/10/25 v2.60 PST-fp' (hv)
pst-plot.sty    2011/04/13 package wrapper for pst-plot.tex (hv)
pst-xkey.sty    2005/11/25 v1.6 package wrapper for pst-xkey.tex (HA)
pst-plot.tex    2014/08/23 1.70 pst-plot' (tvz,hv)
pst-math.sty    2014/07/30 package wrapper for PSTricks pst-math.tex


What makes the issue even stranger is the fact that in the TAN-plot, the problem only appears in the bottom right corner:

Even though this seems to be an Adobe problem, I still ask the question on TeX.SX, hoping that someone knows a workaround. The thing is: my friend has to give the PDF to someone who will print it with Adobe reader, so changing the reader is not a solution.

• I can't reproduce your problem printing with Acrogat Reader DC. – Bernard Aug 27 '15 at 13:11

With an up-to-date TeXLive 2015 you'll get

\documentclass[border=5pt,pstricks]{standalone}
\usepackage{pst-plot}
\listfiles

\begin{document}

\psset{xunit=1.05cm,yunit=1.05cm,plotpoints=200}
\begin{pspicture*}(-1.38,-2.28)(4.19,4.45)
\psgrid[subgriddiv=0,gridlabels=0,gridcolor=lightgray](0,0)(-1.38,-2.28)(4.19,4.45)
\psset{xunit=0.21cm,yunit=0.21cm,algebraic,linewidth=0.8pt,arrowsize=3pt 2,arrowinset=0.25}
\psaxes[labelFontSize=\scriptstyle,Dx=5,Dy=5,
ticksize=-2pt 0,subticks=2]{->}(0,0)(-6.92,-11.39)(20.96,22.23)[x,140] [y,-40]
\psplot{-6.91776797358592}{-1.4000001}{(x^3-3*x^2-6*x+8)/(x^2-3.6*x-7)}
\psplot{-1.399999}{4.99999}{(x^3-3*x^2-6*x+8)/(x^2-3.6*x-7)}
\psplot{5.00001}{22.5}{(x^3-3*x^2-6*x+8)/(x^2-3.6*x-7)}
\psline[linestyle=dashed,dash=2pt 2pt](-1.4,-11.39)(-1.4,22.23)
\psline[linestyle=dashed,dash=2pt 2pt](5,-11.39)(5,22.23)
\end{pspicture*}

\psset{xunit=0.5cm,yunit=0.5cm}
\begin{pspicture*}(-7.87,-8.58)(10.82,6.44)
\psgrid[subgriddiv=0,gridlabels=0,gridcolor=lightgray](0,0)(-7.87,-8.58)(10.82,6.44)
\psset{algebraic,linewidth=0.8pt,arrowsize=3pt 2,arrowinset=0.25}
\psaxes[labelFontSize=\scriptstyle,ticksize=-2pt 0,
subticks=2]{->}(0,0)(-7.87,-8.58)(10.82,6.44)[x,140][y,-40]