stitching in the ditch
 

That doesn't always work for me unless that's all the quilting I am doing on the quilt, If I sitd and then do some fmq inside the block I always end up with the fabric pleating against the sitd seam I bought a class from craftsy and the instructor said it's a must to sitd (all) seams I posted the question to her still waiting for the answer, am I doing something wrong? do any of you have this problem? would like to hear you opinions.

It sounds like the quilt is not basted well enough maybe. How are you basting the quilt?

are you working on a frame or dsm? it sounds like the top wasn't or maybe both were not pulled tight enough when you did your sid.

I took what I think is the same Craftsy class and am having great results using stitch-in-the-ditch (SITD) as she recommends. I wonder if your SITD is somehow too tight? Are you using a walking foot so that your quilt layer feed evenly? As Debra asked, I also wonder if your quilt isn't basted well enough and is allowing your layers to shift while you're doing SITD? By the way, I always spray-baste with 505 spray, rather than pin baste. I don't know if that's a factor in keeping the layers together better since I've never really pin-basted. Anyway, I hope the instructor has some suggestions that will help you. It must be frustrating to go to all the work and then not have it turn out like you want.

I also think that you haven't secured your sandwich enough. Try more pins/spray/glue basting.
Another thing is double check your pressing. If you have pressed tiny folds into the seams, the extra fabric would be released when you gently pulled the seam open for your SITD.
And, finally, you might want to try loosening your presser foot pressure a tiny bit. Too much pressure might create a ripple that gets pushed toward the edge of the block and gets trapped by the SITD.

I think I took the same class too. I use bottom line thread to SITD around all the blocks and then I do more decorative stitching in the blocks or across the entire quilt. A walking foot is important! And getting every layer sandwiched flat and even is important. I clamp my backing on a big table top and I pin baste. I hope you find a solution to your problem. It is so frustrating to get to the quilting and not have the result you anticipated.

I do not understand why you would want to SITD then do more quilting.

I handle stitching in the ditch by staying outside of the ditch. I avoid it at all costs and stick to FMQ.

I have quilted hundreds of quilt starting with the ditch and never had any puckers on the back. Sounds like your sandwich quilt has not been properly laid out and secure.