Maybe use more pins when you baste? Start quilting from the center, if you can. Make sure your 3 layers of the sandwich are "pulled tight' before you begin pinning. Hold your tongue just right and chant..."No puckers," three times.
I am sure you do all of this already, though the chanting may be new to you.
I really can't help, but I thought I would try. I have puckers sometimes too, but I think I am going to, unless I send it out to a LA to be quilted, and I am too cheap for that.
Funny, my husband just brought me hot tea, and he saw this thread was about puckers. He said..."What's wrong with puckers, and puckered up for a kiss." He's fun...
Dina