Adhesive advice- please! - Tile Advice

[foxxcreative]

I’d primarily like advice on the choice of adhesive- but any other constructive comments also welcome!
I’ve got some 600x600x10 tiles coming, they’re going on the floor (separate shower tray), and shower walls, with 3mm spacing all round. The walls are 30mm Aqua board and solid, the floor however...
I’ve battened between the joists at 400mm centres, got 25mm osb, and then 4mm Aqua board (secured with tile adhesive) but there is definitely still movement in the floor.
I’m thinking Ditra membrane first, but have no idea about the adhesives (wall and floor)
And so, any suggestions welcomed, thanks!
Pictures probably don’t help but just in case...

 

[Dave]

Hi. Ditra is for lateral movement, not deflection. You need to address this before tiling.

 

[foxxcreative]

Hi. Ditra is for lateral movement, not deflection. You need to address this before tiling.

Thanks, is there an accepted tolerance?

 

[Dave]

Thanks, is there an accepted tolerance?

A simple test is to fill a glass with water and walk heavily near it. If the water spills you have too much deflection