I'll go out on a limb, and say that what we see is normal.
At 2ms/div, when retrace and trigger times are included, the redraw frequency is less than 50Hz, at 5ms/div less than 20Hz and at 10ms/div less than 10Hz.
Even 50Hz, depending on the persistency of the CRT, can be slow enough to perceive flicker.
This, in the assumption that the chopping in the video be only due to the interference between the redraw rate and the camera shutter.