So it appears there were 2 flags thrown on that conversion, one for illegal touch (Decker), the other for illegal formation (Skipper). Reason for Skipper being flagged is they thought it was him who reported as eligible (which he didn't), so he was flagged because he was covered by Sewell - which would be an ineligible position. Decker was flagged because they mistakenly thought he didn't report, which he did. Seems pretty clear the referee just blundered that whole thing by being confused about the right number/player