Originally Posted by MTS

Well, I'm not German, I can certainly see the problem, and it would bother me, so I can totally see why you want to fix it.

Sandyms uses the same method I do.
I call it "targeted specialized surgery."

Just some random notes from my experience in this field ;-)

You want to gently open the seams around the blocks, extending it an inch or two on all sides.
This will allow the block to gently fall out without any pulling, and still leave you some room to maneuver the new or redone block back into the same space.

Because those sashings are pretty thin width-wise, and solids sometimes tend to fray more than prints (in my experience), I would probably do one block at a time.
That way you keep the quilt top relatively intact and stable while removing and inserting.

Just keep track of where you are on the back and front - I've accidentally opened the wrong seam.
Nothing to do but laugh and sew it back up again.

Try to allocate the couple of hours it will be take all at one time.
I've found it's much easier doing it in one sitting then walking away and coming back, and having to figure out where you where (which, btw, led to opening the wrong &#@&& seam!!).

Work slow and methodically, and you'll find it's really not a difficult process at all.

Good luck!!