It's just a matter of luck whether or not your peep turns properly when it's sandwiched between the two main color bundles. It doesn't always work out that way. We're often required to split several strands of the odd color into the other color bundles. You must make the peep rotate right and you do whatever it takes.

A few guidelines... If you need to turn the peep a lot (1/2 turn or more), twist the top end of the string (it's closest to the peep and will have the most effect). If you need a 1/4 turn, twist the bottom end. Then when you get close you make fine adjustments by moving individual strands. Just move the same number of strands on both sides of the peep to keep the peep centered in the string.