Well the marks are caller chatter and occur because the too, is cutting intermittently. The blank effectively moves away from the tool , for whatever reason and then moves no back and the tool cuts it. To avoid it try turning the tool so it cuts on an angle ( challenging but not impossible to do). Try varying your speed up a bit and take shallow cuts only just touching the surface. I find an HSS roughing gouge often cuts through it as it has weight and does not vibrate ( which is another cause of chatter ).
By cutting at an angle I mean revolve the tools shaft to present the cutting edge at say 45' or in terms of a clock face 1.30 - if you think of the presentation you are using in your video clip as presenting the tool at 3 o'clock as the cutter faces flat along the blank. Hope that's an easy to follow description ?
