nDisplay stuttering

Hi there!
I have a question regarding stuttering when using ndisplay.
Our setup consists of 5 identical PCs which each output to a single monitor (so 5 monitors in total). They are connected with a gigabit switch.
This setup works fine but some of the PCs output a slightly stuttering image. This is a problem as the seam between these monitors and the rest is quite visible.
We think that vsync might be the problem here as the framerate on all PCs is locked to 60. We did find some console commands that we think are related to ndisplay vsync behaviour (nDisplay.render.VSyncInterval and nDisplay.render.softsync.*) but could not find any documentation on these.

Any help would be much appreciated! (: