Porcelain slab joints and gaps

[MidsTW]

I had a garden landscaped a couple of years ago and a few of the joints have come away, it was expected as I frequently jet wash it and it is the resin jointing compound.

However a few of the slabs sound a little hollow And has a tiny amount of movement (they are 900x450) so I am thinking of pouring some type of ‘slurry’ in before refinishing with the resin jointing.

Has anyone got any suggestions for the slurry mix?

 

[MidsTW]

Thinking of using some primer slurry to potentially fill any small voids and top up with the easy joint resin grout that was originally used.

There is a section where the based as moved a little, this is 1 row which wasn’t laid on the same day as the other slabs. What can I fill this void with? Sand and cement?