Blocks shrink after sewing! OMG!!NO!!
 

I cut the blocks the right size but after sewing they are smaller on all four sides. I have measured my quarter inch seam and it is a quarter inch so what am I doing wrong. Rarely spritz/steam while pressigng.

I recommend doing some sample blocks, like 2.5" squares sewn together, then measure. Try using a "scant" quarter inch or other trials until you know exactly where to sew on your machine and with that foot. Remember you lose a little with the fold, so if your stitching line is exactly 1/4" from the edge of the fabric, once it's folded you will lose a bit.

It could be the fold of the fabric, just as fay said. Frustrating when you've sewn precisely, but not taken that fold into account.

I tend to oversize my blocks when possible so I can cut to the perfect size. Sometimes you can't do that. But, doing a test block and learning where your scant 1/4" needs to be is so very important.

How much smaller are they? Plus when you measured before cutting did you add 1/2" total or in other words 1/4" on all 4 sides. Sometimes, and I'm guilty of this, I measure adding only 1/4" on 2 sides forgetting there are 4 sides making my block end up 1/4" off.

If they are all off by a similar amount, it may not make much difference to how they fit together.

I've always heard that to test the accuracy of your seam allowance, you cut three 2 1/2 inch squares and sew them together and then measure the finished product. It should measure 6 1/2 inches and the center square should be 2 inches wide.

I have a feeling that the thickness of your fabric, thread or both are causing the blocks to come out smaller.

I'm experiencing the same with the "Wild Blue Yonder" airplane block - just a smidge short in length on some of the blocks, others of same come out exactly. I have a sneaking suspicion it's due to a computer stating the exact sizes to cut instead of an actual person who would know to advise to cut a smidgen larger to be able to square up each block successfully.
I have tried opening seams that I had pressed to one side originally - that works on most, but sadly, not all. I will have to redo the tail section row, the last row, on some by cutting new pieces 1/4" wider to be able to square up exactly. The width of the block is overly generous, just not the length.
Hope I'm on the right track here. : )

Maybe you have a fabric that is a poly/cotton blend? I used what I thought was cotton from my stash for making churn dash blocks. Once I pressed it I realized from the smell of the fabric that it was polyester. I put one block together to see how it came out and it was off to the point it was useless. Needless to say the rest of the piece of fabric went into the trash. I would never have bought it, so it must have been given to me or part of a grab bag.

Was the fabric prewashed? I had that happen with a RJR fabric that had missed being prewashed. It shrunk enough to distort the block when I pressed it.