Despite taking the Leitch DPS-290 out of the mix, the capture-card seems to have duplicated <10 frames (yes, frames -- not fields!) in each capture. I'm working on manually identifying and removing them, as they interfere with my ability to line-up each of the captures to one another.

The following algorithm outputs ~100 frames for each capture, many of which are false-positives.

c.WriteFileIf("current_frame != 0 && YDifferenceFromPrevious() < 1.0", "current_frame", append=true, flush=true)

I have a Perl script that takes the list of frame numbers and outputs AviSynth code to display: frame-1, frame, frame+1, red frame, .... Identifying the duplicated frames is then simply a matter of visually inspecting each segment and writing down the result. I plan on double-checking these results against something like MultiDecimate before moving on.