This is a very old bug that started happening around 4.9 or 4.10 or even earlier. The grid always looks like this:
http://puu.sh/vbYAW/b12bfe588c.png
This is not how the grid should look like I think, I actually forgot how the correct look of it is since I’m now used to the broken rendering for at least a year. I thought it would just be fixed after a while, but since it never was fixed, i’m now finally reporting this. It’s likely an issue that only happens with specific GPUs, I’m using a AMD R9 390 with the newest driver, older drivers had the same issue.
This is almost 2 weeks old now, has no one looked at it yet?
Hey John,
I apologize for the wait. I can start looking into this for you. You are correct that the grid shouldn’t look like that. I know that I haven’t seen this issue even while using systems with Radeon GPUs. Would you mind providing the DxDiag of the system experiencing this issue?
,
Ed
Strange, I am 99.9% sure that I posted an answer to this 4 days ago. I have uploaded the DxDiag and posted it here, no idea why that comment does not exist now. Either I forgot to click the “comment” button or there’s something wrong with the answerhub 
Well, here the DxDiag is again: https://puu.sh/vrOHI/6497f16902.txt
Nothing stuck out about your DxDiag. This honestly looks like you have an issue with the “LevelGridMaterial2” found in engine content. That is the material we use for the UE grid.
Here is how the material should be setup by default. Would you mind checking to see if there are any changes?
Your screenshot is how the material looks when it is applied directly to a mesh.
Let me know if you notice anything strange.
Ed
Hey Ed, the material has exactly the same nodes here.
I have also tested it with 4.16P1 now, and there the issue does not appear, the grid looks correctly. So it seems it’s already fixed in 4.16 
for looking into this!
