Set happens in all wood bows. Adding reflex helps eliminate that. Also wood that is not nice and dry causes set, " as in green wood ". 12% and under is a good moisture content. 10% is even better.
Set also comes from tillering negligence. You want a nice even bend from pull # 1. The sooner you get that even bend, the better off the bow will come out. Thus limb timing comes to mind.
If one limb is stronger than the other to start, and you keep pulling the bow without adjusting that unbalance. The more you pull that bow, the stronger limb is making the weaker limb, WEAKER.
Ya just developed set in the weaker limb from the get go, if you do not get those limb synced ASAP.
Night Johnny, past my bed time..