I agree with you. After spending any amount of money you want the product to work correctly. I would be on the phone immediately and ask for replacements. I would try to give them information on when you bought the frame, and how long the rails would work before they broke. They can't remedy the problem if we don't tell them what is happening. And how can you use the frame if the rails are cracked.
My frame arrived in December and once assembled, I have had no problem with the rails. The King size rail, which I am not using, was cracked in several places because of being folded. They replaced it even though I am not using it. It came in a large flat box, and was packed so it was not folded so tightly, but actually in a large round coil. I am keeping it where it will not be exposed to cold temperatures. I suspect it is made of some sort of nylon, and old nylon products will crack if they are cold.
You might ask if there is some lubricant to use on the rail to keep it plyable. I have done nothing to mine, but that does not mean that in time I am not going to have a problem.
Please don't put off making that phone call. It will not cost you anything and you want to be able to continue to quilt. It is our responsibility to make any manufacturer aware of the fact their product is not working correctly. They buy the rail materials from a supplier and more than likely they have gotten a bad batch. It is like the light bulbs that came with my machine. They lasted about 5 days. I phoned Bailey. "Skip" (the owner) told me they had gotten a bad batch of bulbs and was sending out new ones when he learned people were having trouble with them. Most businesses want satisfied customers.