Work on nose tipping without the barrels, like in a smaller figure 8. Drop your outside rein, and pull the other side up, and a tad out. Jiggling it usually helps to get them to give their nose as well. Remember to use your leg pressure to tell your horse to BEND and not try to spin. You can do all kinds of response to tip exercises to help with this. Make sure that when you are coming from the first barrel, your reins are slightly slack, and you are cuing your horse to make a pocket at the right time. If tipping exercises don't help, start your pocket a stride or two earlier. Maybe your horse is trying to tell you that they don't think their pocket is wide enough to make a clear turn by pulling to make it bigger themselves. It could also be something as simple as your horses lead when taking off, or that they just don't like turning in that direction. Try switching which barrel you start at, and see if your horse likes it better.