It may not be anything, but don't sim the nodes in one big bunch. I sim 2-3 at a time and watch the shards climb. Vet Chewie is 7*, and Vet Han is half way to 7*. Also as a side note. If your spending thousands of crystals to farm them, once you get to a certain point just spend the crystals on their shards in the store. It's guaranteed that way. So instead of spending a couple hundred crystals hoping to get a few shards, just spend 680 to get 8. Hang in there, the drop rates aren't bad, but don't expect to get 80+ shards on 5 refreshes