To help us understand and resolve your issue please check that you have provided
the information below.

• Matplotlib version, Python version and Platform (Windows, OSX, Linux ...)

Platform: Debian Testing, using the python 2.7 (2.7.11-2 when I first started seeing this, just upgraded to 2.7.13rc1 but the problem still exists). I have this problem with the 1.5.3 on debian testing, but I also tried a virtualenv with pip install --pre matplotlib, which pulled in 2.0.0rc1, and I see the same problem.

Debian stable, with matplotlib 1.4.2, works fine, as did Debian testing until recently.

• How did you install Matplotlib and Python (pip, anaconda, from source ...)

See above: Debian package and virtualenv.

• If possible please supply a Short, Self Contained, Correct, Example
  that demonstrates the issue i.e a small piece of code which reproduces the issue
  and can be run with out any other (or as few as possible) external dependencies.

Minimal test program:

import pylab

distances = [0, 0.0011970407617050934, 0.0050796062254631295, 0.007303941153223762, 0.007303941153223762, 0.008232870398475445, 0.008232870398475445, 0.012806461740481582, 0.016651523629144134, 0.021047330616832543]
elevations = [6404.2, 6410.76, 6400.92, 6410.76, 6423.88, 6423.88, 6453.41, 6410.76, 6427.17, 6420.6]
pylab.plot(distances, elevations)
pylab.show()

(Please let me know if you want a non-pylab example. I see it with straight matplotlib too.)

• If this is an image generation bug attach a screenshot demonstrating the issue.
• If this is a regression (Used to work in an earlier version of Matplotlib), please
  note where it used to work.

It worked as recently as a month ago on Debian testing, but sorry, I don't know what matplotlib version that was since I didn't know it was going to stop working.