When season ends in next couple weeks - let me take a look at that board.
I've ran them in some serious slop and never had trouble.
I'm thinking like you - combination of 3-4 things that caused it to flip. The tow line clip getting cocked can make a board pull wrong.
I did have a stick get jammed in between 2nd and 3rd board once and caused board to act wrong. Luckily - it came loose before causing board to flip.