How do i stop invisible collisions on a barren flat surface?

Hi Guys and Gals,
I have a rather peculiar problem where by I get collisions on flat surface that does not really exist.
I am building a sliding puzzle, out of a grid of physics boxes.
And when sliding the boxes over the surface of the grid so to speak I get collisions on the edges of the boxes underneath (where two grid pieces meet) and the sliding block so to speak gets stuck on the flat surface unwittingly trapped by a volume below.

I’ve seen people talk about reducing the min and max thresholds of physics to reduce the effect of seams or overlaps but this seems to not work for me.

I have tried turning on sub stepping as well as an option but both these dont seem to fix the issue.
Is there a way to either merge physics volumes like boolean Addition, or baking the physics of purely static models into the scene to make this simple problem work.

In my test I push a box across a flat surface and 1/3rd the way across the open area it bounces back as if it hit a solid object. (at a seam)

Thanks in advance