Patio grouting easyjoint problem

Hi all my dad's just done the grouting in the garden he's used the same product easyjoint as I used over a year ago but after 2 weeks it's cracking and coming back up.

When he moved in the previous owners had tried to do the same and it was cracking and coming back up,so he cleaned it all out etc.

Any ideas what's gone wrong?

There has to be movement in the patio slabs

ktuludays said:

There has to be movement in the patio slabs

Click to expand...

Your right just been round to check them and you can see they move a tiny bit.