Strange Plasterboard Ceiling Support, Repair

[Maksim]

A corner of plasterboard ceiling in my garage is sagging and cracking.

 

Shining a torchlight, I see the boards have filled screw holes for attachment at other points. Only at this 1 edge are the boards held up by 'hooks' every ~20cm (other 3 edges of the garage do not).

 

At the exact spot/line of the sag, I do see wooden batten underneath (thru a small gap at the edge). So what reason could there be for this strange setup? It'd be much easier for the original plasterer to continue hammering screws to the edge, why go to the trouble of installing the 'hooks' as support? It's not a temporary support, as the cornice/architrave have gaps deliberately cut to accommodate the 'hooks'.

 

Anyway, I'm thinking of pushing the board back up, adding screws into the batten at the edge, then re-plaster/paint to finish. Is there any risk to trying this fix?

[ProDave]

A lot more than one fixing has failed there.  The only way to be sure what is happening is take part of it down or at least cut an access trap to have a look.

[twice round the block]

Why have you got coving in the garage? 

[Mr Punter]

The only downside will be screwing through any pipes or wires or possibly disturbing an asbestos ceiling above.