There can be many things that cause peep issues. Here are a few that can be the culprit.
1.uneven strand tension during layout process. Becareful to use just enough tension to keep the strands from sagging 1 lb to 1.5 lbs is plenty.
2. Serving to tight. Serving so tight it creates preload on the bundle underneath the serving will cause peep issues. Some will take a piece of painters tape and wrap around the bundle. Watch the tape when adding serving making sure it doesn start twisting the bundle.
Some bows have a sharp ang and can cause serving separation. A different servings or liquid lok can be applied to stop separating servings.
3. Serving wrong direction. This can get confusing so I take my hand a try to add twist to the string and that will be the direction I serve
4. Sliding the peep up or down the string after string is installed. This is probably the main cause of peep issues. Always remove the peep and reinstall after the bundle has gone back to normal. This sliding the peep will act like more or Lea twists on each side of the peep.