Dimension Issues

To make a long story short, when using Dimension on my brand new iMac with the following specs, and adding custom Substance materials to the model, Dimension creates an enormous file size (over 6GB) which becomes unworkable (Program freezes) )and really shouldn't happen in the first place given the fact that my scene and 3D object is simple that all my assets are fairly low weight.

Note that I have re-installed the program as well as created new documents who all displayed the same issue after a while.

Mac specs:
iMac (Retina 5K, 27-inch, 2019)
Processor: 3.7 GHz 6-Core Intel Core i5
Memory: 16 GB 2667 MHz DDR4
Graphics card: Radeon Pro 580X 8 GB

Doc set-up:
1920x1080 and 3840x2160 both at 72dpi

Assets:
3D model I used is only 1.1MB in file size.
The textures I used are 89.1MB, 30kb and 16kb. 

I tried both .fbx and .obj, but again the 3D model is a desk and it works fine when imported into other rendering software such as Marmoset toolbag.

Note: My machine doesn't have the option:" Disable 'Automatic Graphics Switching' option"

After opening several support tickets, the support Rep said I would need an update to my graphic card's driver. It seems odd that this would be needed, given that this a brand new iMac. Also, when I looked at: https://helpx.adobe.com/dimension/system-requirements.html my graphic card doesn't look supported, it only lists nVidia GeForce RTX 2060, or Quadro RTX 3000. 

If this is the case, I am puzzled as most people on a Mac won't have those graphic cards installed as Apple doesn't support them.

It's either that or the program has a serious bug and wrongly calculates added custom Substance materials (generating a massive file) every time it's being added to a surface. Since custom substance materials can't be saved in the library they have to be dragged and dropped onto the surfaces individually.