I've found a few solutions. First mine always works if I start from the right side of the trackpad. Then after that works the centre starts working but the left side usually doesn't. However I figured out I usually do the gesture with my 3 fingers making a diagonal 45deg line. If I move the fingers to a straight line configuration it works everywhere. I tried putting them closer together but didn't make it any better. Only changing the angle of the 3 fingers makes a difference for me.
It is a little weird but now that I know how it works and doesn't work I can adapt for now but hopefully Apple will tweak the algorithms....