Tile question

I laid ceramic tile over a concrete slab - new construction. There was a crack in the slab before any tile was laid. I was told by a local tile guy, to use a rubber membrane brushon coating to cover the crack.
I did this as instructed. The specific product I used was called Pro-Red Waterproofing Membrane, "elastomeric waterproofing & anti-fracture membrane". Part of the product description even states, "reduces crack transmission in ceramic tile or stone..."
Everything has been good for about 3 years. A couple of months ago I noticed a cracked tile, and put it on the "to do" list. Last week, it had spread to include 3 tiles total. So I decide that today is the day I will chisel the tiles out, coat the crack with the membrane, and lay new tiles in a day or two.
Imagine my surprise when I begin removing the tiles and discover that they are some of the tiles lying over the already coated crack.
So now I am essentially back to the beginning - sort of. If the membrane didn't stop the tiles from cracking the first time, what would make me think a reapplication will be any different? Based on this, can I expect the tiles along the other 25' of the defect in the slab to likewise crack over time?
What can I use to prevent future cracks in the secton of slab that is now exposed? What, if anything, can I do to prevent other tiles that are currently laying on the slab, over the membrane coated fault line, from cracking?
Thanks for any help.
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Check to see how much movement you have at the crack. You may also have a large enough field of tile to require an expansion joint. Robert A. Cibiras wrote:

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The slab must have shifted and overcame whatever crack resistance was offered by the membrane. What kind of thinset did you use? How far past the crack did you apply the membrane?
I tiled over a crack in a bathroom using Custom brand Flex-Bond polymer modified thinset. They offer a substantial warranty against cracking if used along with their own membrane, but it is supposedly the combination of the two that is important - the membrane plus the polymer modified thinset.
-rev
Robert A. Cibiras wrote:

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Id be focused on the fact that you have movement rather than how to fix the tile for now. Because next or eventually it will be the doorways then the drywall, plumbing, ect.

Sounds like the red membrane (looks like very thin red fabric set into the coating while stil wet) is part of the system you left out or di I not read it correct?
Robert A. Cibiras wrote:

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