Good eye - yes it was bouncing, and I don't really know why. In truth I did not feel it thanks to the A/V system, but I saw it in the video. Curiously, I have another video (that I never uploaded) taken right after in a larger piece of the same tree, and it does not seem to be doing that as much. It might be because the saw is running at a slightly lower rpm in the larger round - maybe there is some sort of resonance going on, with more vibration due to higher rpm and lighter bars? This bar is cheap and light.
I can post that other vid later if you want, but it isn't too interesting otherwise.
I remember your earlier comments on VXL loops chattering. I have a 68DL loop of VXL on another ported 42cc Poulan and it was very smooth from the factory grind through several filings. Then I used the wrong gauge which set the depth gauges just a little too low, and now it's fairly grabby and bouncy. And that is a heavier, longer bar. I suppose it is possible that I made the same error on this Tri Link loop.