I just finished quilting one with the same problem. I'm not sure why/how it happened. I'm not that experienced at quilting, but it has not happened on the few quilts I have quilted previously on my domestic sewing machine with a walking foot.
Sometimes, I don't think you can fix it. If you spray basted it, it's only going get worse if you try to reposition it now. I think, but am not sure, that all that sewing, resewing, positioning and repositioning can stretch your fabric and result in more "puffiness" somewhere else. So, you just end up moving the "puffiness" around.
You will have to decide how important it is to you. I might measure the area that is "puffy" and compare it to the same block in an quilted and unquilted area. If it's the same, I'd leave it. If it is smaller, I might re-do it, as it's going to pull other areas out of line. Your ruler will tell you how much it's off.
On this one, I'm just going to wash it before it's gifted. Hopefully, that will help. If not, I'll keep it for myself, as it's still a pretty quilt.
bkay
Second thought: Try taking out every other row.
Last edited by bkay; 09-04-2018 at 06:16 AM.
Reason: second thought