I have noticed this after the latest Client update. I have determined that this is only a problem in Future lighting with parts that have reflectance set.
To reproduce this problem, use Future lighting, set a smooth plastic part’s reflectance to .1, publish and play test the game in client, the part will be black.
The fix if you’re having this problem is just to set the reflectance to 0. I tried to submit a bug report and hopefully they’ll fix it in the next release.
This seems to be intermittent. I changed my games to Shadow map to ‘fix’ this. Then today I put them back to Future and the problem had gone away. Now it is back, I even reproduced it on a test baseplate: