You are right on. Wilcox, Lang, and Wright had stepped off as ordered on July 2nd. The Georgians got into some confusion with Federal sharpshooters that had positioned in some out buildings on The Brian or Codori Farm. When Posey and his Mississippians didn't advance as ordered, Billy Mahone's Virginians didn't either. This broke down Lee/Longstreet's en echelon attack that until that instant was crushing the Federals brigade by brigade and rolling up the line. Barksdale's Mississippians had slaughtered the Federal defenses down the line and had captured several artillery pieces. The subsequent wounding of Dorsey Pender as he sent out skirmishers to renew the attack spelled the end of the day's success for the Confederates. This was probably the key aspect of the fighting at Gettysburg that caused the Confederate Army to not win the field that day. Had July 2nd continued as it had started there may have been no Picketts Charge.

Keith