Advice on repairing 3 tiles

[tubelloabril]

Hello. I need your help again please. I'm due to remove this 3 cracked tiles which have cracked for the third time after having replaced them 3 times (picture). I'm not planning to re-tile the entire floor but just the 3 always-cracking-tiles. What would you recommend to do? What should I install below those 3 tiles to prevent cracks forming, considering that the floor around it won't be touched? If I use an uncoupling sheet for them it won't be levelled in relation to the rest of the floor. What do you think? The subfloor is made from concrete.
Thanks!

 

[Dave]

Remove the tiles first and see what’s happening underneath

 

[Ajax123]

until you figure out what is causing the cracking you cannot fix the problem. theyve cracked in the same place 3 times. if you dont figure out why and fix it then youll simply be replacing them again a 4th time. As Dave says.... ift the tiles, see whats happening underneath and go from there

 

[tubelloabril]

Thanks. But what if the concrete slab underneath them is cracked? Will I have to remove all the tiles or can I fix the problem of this 3 by using a flexible sealer or something like this?

 

[Ajax123]

If the concrete is cracked repair the crack with a proprietary repair system like kr516 from uzin