The center I bowl at almost always produces the same thing. I have never quite figured out why. But even when I throw an old urathane nitro, I have the same problem. you can see the oil where the track is, but there also tends to be a light film of oil on the rest of the ball.
Make sure you have a microfiber towel or 2 to keep the ball dry. They seem to remove this file fairly well for me. Though it doesn't stop the oil getting in my thumb holes, thus producing several poor releases a night. If anyone knows the cause of this, I too wouldn't mind hearing it
