Outdoor porcelain lifting help

[Blobber45]

Hi all,

I had my patio done with porcelain paving a while ago and one of the slabs has a little movement on the corner, like there is a 1mm void underneath the slab, causing the grout to crack.

Nearly all of the slab sounds completely bonded, it is just this corner that sounds hollow.

Is there anything I can do to sort this without having to lift and re-lay the slab?

Thanks!