when your quilt is 'loaded' to be long-arm quilted it is stretched tight and smooth across the quilting area. this puts lots of tension on the seams in a pieced quilt. i have noticed often interior seams pull apart. i usually try to 'fix' them as i quilt but at times it is too much for the quilting to take care of it. in those places i put some sort of (mark) to identify the spot so repair can be done after the quilting. it can be from thread breaking as easily as from not being secure in the first place. i try to kind of pull on areas of my piecing to make sure seams are not coming apart while i am constructing so i can identify problem areas before loading it on the frame. your fix sounds like a good one.