[old_tv_nut]

To get clearer scope traces:

Set horizontal sweep to 10 us / div. This will display somewhat more than one video line period (=63.5 usec)
Set vertical gain to calibrated position so you are not reading an unknown amplitude such as > 1 v/div ("greater than").
Adjust trigger level to trigger on H sync pulses

All you can tell from what you have posted is that you have video (but you knew that because you have a picture).

Then, if you can put up a still image that shows the white smear following a black block on a plain background, you may be able to see it on the scope, and see which places in the circuit it appears. If you don't have any test pattern sources, try to find a DVD that shows the problem when you pause it.

Edit: A still image will also allow you to see the effects of any adjustments without getting confused by varying video content.