[old_tv_nut]

1) only happens with one DVD? Then it's the DVD. Looks to me like the DVD may be a copy of a videotape that had some defects.

2) Since there are similar coils in R,G, and B circuits, you can compare them. One way to detect a shorted coil would be with an ohmmeter, but the low resistance values may be hard to measure accurately. Another thing you could try is connecting a short wire across a coil in the red or green circuit and see if it gives the same effect as you see in the blue. If it does, then try shorting the corresponding blue coil to verify that the added short doesn't change the problem; in other words, the coil in the blue section was already shorted. Of course, I am only guessing about the possible cause, and you may find that the coils are OK and the problem is something else.

3) If you're not seeing a beat pattern, the best bet is that the adjustment is already optimum, so just leave it alone.

4) Caps that would affect the alignment are small pf values associated with IF coils/transformers, and seldom fail, so are not usually replaced when re-capping. Typically needing recapping are electrolytics and paper caps with much larger values, like nanofarads (thousands of picofarads) and upward to microfarads. If the picture and general operation of the set is OK, alignment is not needed, and is only an educational exercise.