Grout between floor tiles keeps breaking up

[Beemer]

The grout between our bathroom tiles keeps breaking up in one area. I'm pretty sure it's where a joint running along the 'no more ply' is directly beneath the grouted join.

Each time I scrape out the old grout and regrout.

Other than ripping everything up and laying new backing board and tiles (making sure that tile joints do not run in line with the board joins), is there any other solution?

 

[WetSaw]

Colour matched Silicon instead of grout if it's only one grout line.

 

[Unused Account 1]

The sub floor ,could be still mving ,not screwed down enough maybe

 

[Time's Ran Out]

No more ply!!
I’am not a fan.

 

[Unused Account 1]

Never used it

 

[GoneGuy]

I found no more ply brittle compared to hardiebacker

 

[John Benton]

I found no more ply brittle compared to hardiebacker

Thats why I stopped using it, also I found it was very shiny, which by default is difficult to key to

 

[Waluigi]

Last few jobs I’ve been using Orbrey Pro Ply. I swear Hardiebacker is a health hazard. At least Pro ply is Silica free.

Also, I think it can be laid over wet UFH systems.