Inconsistency displaying space between objects

I imported an fbx made in blender. This simple test, the fbx just contains four squares with thin space between them. However, depending on the positioning, the space appears perfectly, appears for some objects or doesn't appear at all. Attaching screenshots. How to solve this issue?

 

This will be due to rasterisation, resolution and perspective. It's perfectly normal. Your computer doesn't have infinite resolution, and the gpu has to make the best decision it can to place a pixel.

Using textures instead with alpha channel and anisotropic filtering will enable the gpu to make a better guess due to it having more data (mip maps) to look up a relevant pixel from.

So if you're doing this, it's probably better to use trilinear filtering + anisotropic turned up with textures. Alternatively, you could render the mesh to a texture, which is guaranteed to show the gaps as you'd like (only need to raise texture res until it does) and then render the texture. Providing it has mip maps, it should pick a relevant pixel quite well.

High quality antialiasing can enhance some details too - you'll have to play around but this is the nature of the beast.