Is it possible to have a "bad batch" of needles? It seems that out of the blue, the box I'm currently using has some bad needles in. They almost feel barbed as they go in and occasionally draw blood. Maybe 1 in 3 are hurting quite badly whilst the others glide in. I'm rotating sites etc and it's not the injection, just the insertion of the needle. Has anyone else had this? It's like Russian Roulette 
