Cracked row of tiles over dodgy boarding

[happybudda]

Hi Guys, first post.
Have recently tiled upstairs bathroom in a new build.
Boarding looked bad so pointed out to owner.
He said to just add screws to tighten up boards.
Laid tiles using a good flexi adhesive.
Couple of weeks later row of tiles cracked over where boards underneath joined (25mm ply). Builder blaming tiles as he says double joisted etc.

Without having to remove all tiles and reboard, could i just strip out row of cracked tiles (12x12 slate) and replace with a nice 12x12 row of slate mosaic. The thinking behind this being that mosaic might stand up to movement in boards. Any help appreciated

 

[gcol]

Instead of the tile cracking you will end up with grout cracking. You need to ensure the floor is sound.