[swarmee]

Yeah, correlation does not imply causation, as I learned in science. They could be an interim printing stage, but they're much more likely to be a replacement of the printing plates with their own flaws, IMO. Which those were then further corrected.

Add: I recall someone saying that Topps likely had 7 printing presses, with each needing a set of plates. Not sure how true that is, but this could show that one set of plates had one set of errors (regular NNOF and other blackless partial border/background cards), then a different set of plates had these errors you're spotting (two gaps Frank Thomas, Tapani gap).