Loose dot and dabbed boards on facing bricks

Looking for best way to secure the loose plaster board to house 'facing bricks' as dot and dab loose from board so bit of movement.

Heard best way was few pilot holes and use some grab adhesive expanding foam, if so any suggestions what one? Also am I best to push against the board to stop it popping out so it grips wall and board too? Had a tip to put a screw into adjacent board to prevent popping out of place.

Was wondering if there's a way I could bypass the foam and secure with screws and plugs? Anchor fixings look as if they would do the trick? Mabey a washer on end too to spread the force on board?
 
Looking for best way to secure the loose plaster board to house 'facing bricks' as dot and dab loose from board so bit of movement.

Heard best way was few pilot holes and use some grab adhesive expanding foam, if so any suggestions what one? Also am I best to push against the board to stop it popping out so it grips wall and board too? Had a tip to put a screw into adjacent board to prevent popping out of place.

Was wondering if there's a way I could bypass the foam and secure with screws and plugs? Anchor fixings look as if they would do the trick? Mabey a washer on end too to spread the force on board?

Foam.

@ET
 
Foam.

@ET
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