Getting rid of reflection flickering with mental ray MIA material in maya 2012

Today I ran into a very weired phenomenon.

I have a floor that is shaded with a mental ray MIA material. It's reflective with some 0.5 gloss, enough samples to keep it smooth and an anisotropy value of 0.5. I render with the maya 2012 integrated mental ray version. No plugins.

When I distributed the scene to my render farm, I had the strangest flickering on the floor. I searched for quite some time. Now I have the solution to the problem:

Some of the render nodes straight out ignored the anisotropy value of 0.5!!!
I could not find out what caused this, since all the nodes have the same specs and were bought in one batch (so same hardware, same OS, same maya version, etc.). I also noticed, that the mapped anisotropy value of another object was rendered correctly.

So the workaround for this bug: Instead of just using the slider for your anisotropy value, just use a greyscale image instead and map it to the checkbox next to the slider.

Also, don't forget to check "alpha is luminance" under "color balance" in your grayscale image's file settings within maya.