I've found out there's a hard-coded bug somewhere in the converter, not sure if it's the primitives converter or the FBX converter tho.
You don't need to modify anything in the model. To reproduce the bug, just "Export FBX" of any tank, and then import the very same file back by using "Import FBX" and then "Write Primitives" to the actual game folder, re-select the tank in the garage and see the difference: Where comes the lighting from the sun, is actually dark. Any model exported & imported by the TankExporter will be affected because no 3rd party software were involved while producing the bug.

Ill check this right now...

I just tried this with the T110E4 and there is a lighting problem....
I'll look in to this now.

OK.. I found the problem.. Its the surface normals. I fixed this issue long ago and not sure why its happening again but I'll sort it out.. Keep an eye out for version 32.

All fixed! Thank you for reporting this! Not sure how I didn't notice it .. LOL