Flickering blue lines throughout frame?!?

I have some footage with numerous thin blue flickering lines throughout the frame. These are maybe a couple of pixels high; mostly they?re all the way across the frame. They last a field or two, are gone for a random number of frames, and then recur in the same places. By and large they?re all blue, although the lines over light coloured subjects are light blue and the one over red or dark coloured subjects are dark blue. IE they?re partly translucent

There?s lots of them, too- IE No manual painting is gonna work. I figure it has to be a full-frame fix that I can apply to the whole shot. And of course, last but not least, I got about half an hour of this stuff.

Because they?re all variants of blue, and I don?t have much else blue in the frame, I?ve been trying variants of chromakey for a possible fix, replacing the keyed material with pixels from a lower layer offset by a few frames. I couldn?t get the FCP keyer to select the light blue lines, so I used the selective colour corrector to select these, and made them all a nice full blue. The chrome keyer could then key a fair amount of these out.

Where it works (75% of the time or so) , it works great- the lines disappear. Where it doesn?t, it?s truly ugly. The lines that are left are all now dark blue, highly visible, and they flicker like demented neon. Tried a number of passes, but the artifact count climbs too high.

I suspect I?m gonna have to write the footage off, but thought I?d see if anybody has any other approaches, suggestions, or ideas. I do have a question, too: I?ve been replacing the keyed material with pixels from a lower layer a few frames offset in time, but because the lines recur in much the same spots I?d like to try material from the same frame, but offset by a few pixels. Is there a way to nudge the lower layer up or down by a countable amount of pixels?

BTW the footage happened in the middle of a tape. Previous footage is fine. Footage shot on a different tape immediately afterward is fine. I suspect a fleck of dirt lodged in the heads. (Guess I should?ve done a gate check?)

Thanks in advance
randy

highly recommend Martin Baker's fabulous DH_Dropout for this kind of work.
[www.digital-heaven.co.uk]

Many thanks for the pointer.

Tried the demo. Works a treat for some of it, but I think the damage is just too severe. Whole frame attempts start to judder, and there's just too many lines in too many random places to contemplate a line by line fix. (life is too short, and even if it weren't, I start to run out of clean fields...)

I will add it to my solution bag, though. Thanks again.

randy