Originally Posted by Kas
Pin more. Put a pin through the intersection, but just put it straight through so it is sticking out the back. Then put a pin on either side of the set pin and secure the fabric with those. Now remove the first pin. See if that helps with keeping it in place. If you have already been doing that, then I don't know! LOL! Good luck!
Great advice! I'm going to note this in the "quilting hints" notebook :-D