Grout lines cracking

i recently bought an older home than is off of the ground. my kitchen has ceramic tiles and the grout lines are starting to crack in several places. some places the grout has actually come up in small chunks. i am sure it is because the floor under it wasn't prepared properly before the tile went down and the floor does have slight movement.

is there a solution that doesn't require me ripping out the existing tile and re-doing the whole kitchen. this may sound stupid, but is there a type of grout that has flexibility and/or mobility? the tiles are holding to the floor very well. they won't budge to be honest.

 

The only fix would be to redo it correctly by finding out why there is movement in the floor.

 

first of all thanks for the reply....

it that it appears to be movement in the floor under the tile b/c it was laid on top of two layers of vinyl tile (plus the house is 60+ years old). i don't think the subfloor is moving much if at all.

the true problem is that i dont' have the money to rip all the flooring and lay it back down. i was hoping there would be a more simple solution.

 

Sorry, there is none, 2 layers of vinyl huh, the only fix is to rip it all out and start over, sorry.