JAC REFL beam seems to be flickering in the video because the 809Hz length dither frequency is close to the integer multiple of  the video refresh rate. I disabled the 809Hz length dither momentarily and the flickering was gone, see the attached video.

If we can see the effect of the dither just by using the video like this, the length dither amplitude is probably too large to enable in observing. One omega peak observed by ISS array is huge.