This is almost always caused by either:
1) The "Sparkles" setting on the Color panel - although I don't believe that is a full on.
2) An overlap in channels. Turn on the checks on the layout tab and click on the minitree and see if something turns Red.
3) An effect also on that model/node. Depending on the master view order, the group could be rendered before the individual model so the effect on the model/nodes would take precendent. The fact that it "moves" means it's like a twinkle or a strobe effect or similar that has a randomness to it.