Note : -both- bridle ties need to be fastened to the pair of vertical rods on each side, this may be your problem as I have run into 2 blasts so far where it was only attached on one vertical, each side. it'll make a huge difference to the control, promise.
ive had my blast for 6 months and i flew it in a 14 mph wind once and never did it again i found it to be a great kite for the lighter winds almost an oversized ultralight i only pull it out when the winds are 2 to 5 mph i made adjustable leaders for it and they do control pull a little bit