Each one of those looks off by the same amount on each opposite side... meaning something is really wrong. Re-align everything and start from scratch. Also, running a 5x5 piece of ply through the saw isn't fun. Rip it down the middle first - 2.5' wide piece is much, much easier to handle.
If it really was technique, you would have more severe burn marks and mistakes don't repeat themselves precisely and in straight lines.