Yea, I always use Oracal 651. I just cut about 500 stickers at my friend's shop the other day, same pattern, oracal 651, flexi 8.1, just a graphtec machine. I even tried some Avery A-5 I had sitting in a box as well. No matter what I use, it comes out like this.
I just got the machine yesterday, and the headache it's giving me is making me want to return it already.