I had issues with storm bags, 2,3, and 4 ball rollers. Their ball cups and bottom compartments did scratch my equipment. I've had ball cups mailed free of charges to my address. But I got tired of calling them and sanded down the edges where it felt sharp.  Also, throwing or roughly placing your balls into the bag can damage these ball cups. Once I was aware of this, I had no more issues.

My black 4-ball Storm bag had the same issue.  Storm bags have had this issue for years.

I did this years ago...  Just place some heavy duty tape over stitches where the balls are being scratched and your problem will be resolved.  Once I put the tape over stitches, the scratches went away for good. 

Peace!   

I did the gorilla tape method, but it get too messy after awhile. I threw away those cups. Storm is really good at customer service. 5 year warranty at times extended even further. Last 4 ball roller needed new ball cups and an axle, called up storm and gave them the part numbers and they shipped to my address in less than 4 days. No charges.

I added my own wheel bearings and this 7 to 9 year old bag was rolling nice again.

I had issues with storm bags, 2,3, and 4 ball rollers. Their ball cups and bottom compartments did scratch my equipment. I've had ball cups mailed free of charges to my address. But I got tired of calling them and sanded down the edges where it felt sharp.  Also, throwing or roughly placing your balls into the bag can damage these ball cups. Once I was aware of this, I had no more issues.

I use Lane Master see-saws (got them free with my original LM ball purchases) to protect the balls in the plastic cups and to help pull the balls out of the bottom compartment.