Advice needed on bathroom overhang

[YaBollix]

I've installed 10mm Moleanos stone throughout my bathroom and I'm a bit worried about an overhang area where the tiles are fixed upside down.
The sub is OSB which was properly primed and the stone was supported for 24 hrs while it cured. I used a BAL flexi product as the house is prone to a bit of movement being a Victorian semi. Been up 10 days and I notice cracks around the grout line but the tiles seem to be stuck ok, with upward pressure moving them half a mm or so, not really closing the grout crack.
Should I pull them off and redo or is another solution better? I had an idea of drilling some fixings to anchor to the ply base but don't want to ruin the look. Bit concerned about a 2kg tile falling on someone....
Advice appreciated. Andy

 

[YaBollix]

Enclose some photos... Andy

Broken Link Removed

 

[SJPurdy]

I remember doing a job years ago. 40+ toilets (M,F,Disabled) in an office block referb - all on OSB - the tiles didn't fall off as stuck on with BALflex however at almost every joint between boards the tiles cracked due to the movement in the OSB. This job probably why BS now says don't tile on wood based substrate walls except small areas of ply (like pipe box) where no joints.