The 2 biggest mistakes I see are
1. No board down. You need some board in the water. The windward works best because if it you put to much down and touch the crew is right there to pull it up a little bit..
2. Skipper goes to the back of the boat to lock a rudder down and during that time they are not concentrating on driving the boat. The boat either stalls or starts to round up. Keep the boat moving. The last thing you want to do is get hit by a wave with the boat stopped.