Did you test all of the GeForce GTX 1070 DP out ports?
Did you test another DP to DP cable?
Did you test an HDMI to HDMI cable (no G-SYNC) and see the issue?
The full 20 S/N is not private or tied to you. What is it?
What was the different PC specifications as far as Nvidia video card?
You posting a video of the issue with G-SYNC on and off showing the issue would help.
Read this if you have not already.

• Did you test all of the GeForce GTX 1070 DP out ports?
  • Yes 
• Did you test another DP to DP cable?
  
  • I don't have access to another DP cable except the one provided with the screen.
• Did you test an HDMI to HDMI cable (no G-SYNC) and see the issue?
  
  • The issue is even more visible through HDMI since the screen refresh rate is only at 60hz.
• The full 20 S/N is not private or tied to you. What is it?
  
  • CN-07CJHF-WDC00-83U-03RU-A05
• What was the different PC specifications as far as Nvidia video card?
  
  • It was a MACBook Pro 2018 with a DP adapter
• You posting a video of the issue with G-SYNC on and off showing the issue would help.
  • I have a video W/O G-Sync and it's the same result with G-Sync, 
  • https://www.youtube.com/watch?v=_6mYQMJzPlw&feature=youtu.be

83U = Built on March 30, 2018. So almost 6 months old.
When was the purchase made?
Was this purchased directly from Dell?

The testing on the non-validated proprietary Apple does not apply. The first thing you should do is purchase locally another DP to DP cable and test it. Perhaps our DP to DP cable is the problem. If the other DP to DP cable has the same issue, see this.

I purchased the monitor on August 27th, 2018 and received it on September 4th, 2018.

It has been purchased directly from Dell's website.

I'll try to get another DP to DP cable.

Thanks,

I'm experiencing the same exact issue with a different DP to DP cable that just cost me 24$ CAD. At this point since I'm inside the 30 days of purchased and I'm dissatisfied with the quality of this product, I would like to return it.

Like I said in my first message I sent multiple message to Dell support to return my product and no one replied. 

Can you help me accelerate this procedure since I only have 30 days?

To return the item, fill out this online form. Or you may contact Order Support via Chat or Phone to walk you through the return.

One last thing, is this issue normal? Could it be fix by replacement panel? I have you ever heard of it from other users that having this monitor?

Thanks,

I believe it is normal :). I also have the same issue.

Actually, it is not normal. I can tell you that.

A month ago, October 2018, I bought my first AW2518H was manufactured in June 2018 Rev A5. It has a really bad Pixel-Walking / Pixel-Inversion with many dead pixels.

I called Dell for a replacement unit. The second unit was manufactured in June 2018 Rev A5 too. This new screen has zero dead pixel and it doesn't have any pixel-Walking / Pixel-Inversion with the DP at 60Hz to 240Hz and the HDMI at 60Hz with G-Sync on/off. This unit work perfectly at any settings on PC and console. I can’t be happier.

November 2018, I decide to buy a second AW2518H. The monitor has a manufactured date September 2018 Rev A6. No dead pixel but there is Pixel-Walking / Pixel-Inversion in both DP at 60Hz to 240Hz and HDMI at 60Hz with G-Sync on/off.

Even if this is the Rev. A6, Dell must figure out a way to have a better-quality control on those AW2518H because this is not acceptable. Not only it gives you headache when you play, but now you will have another headache to manage a return.