I, too was having this same issue with DigiBeta deck, FCP and AJA Kona 2 card. Never happened before (even on long captures). After trying 3 different decks to no avail, then reading this post and realizing the issue seemed to be with RS422, I simply changed cat 5 patch cable (I run from my suite to an equipment room, where control can be switched to different machines through a patch panel).
Anyway, that did the trick. So, be sure to have “clean” RS422 paths.
Chris