Flickering graphics with new video card

This is a tricky one. I bought a new video card, a gtx 1660 super and using my existing display port cable gives me this weird flickering on the bottom half of the screen. The cable works fine with my old card. I then tried a standard HDMI cable and the flickering problem is completely gone. I don't have another display port cable to try unfortunately. Is it feasible the cable is faulty with one card and not the other? I'm tempted to return the card as faulty but maybe it isn't.
Any thoughts greatly appreciated.
Cheers

Just buy another DisplayPort lead of decent quality.
Pre-made leads generally have poor quality control and the chances of a duff lead is quite high. So much so that I always buy a minimum of two when I need one...

It could of course be the DisplayPort socket on the Graphics Card. Visually inspect it. Wiggle it gently a bit that sort of thing.

Thanks.
The new card has 3 display ports and 1 HDMI. I've tried all 3 display ports, no joy so I ruled out the port being the issue. The current cable/lead works with my existing card so seems strange that it could be faulty. My understanding of cables/leads is that they work or don't, no in between. Reluctant to shell out for a new display cable if that isn't the issue but might have to I guess.

Ended up buying a new DP cable and problem still there so by default must be the card. I've returned the card as DOA and still waiting for replacement.
As an aside. My main monitor stopped displaying today. Tried every fix i could but it wont display using the DP cable. Tried the HDMI port and that works. Seems a little coincidental that the DP display on my old video card has no failed as well. I've never had an issue with this before. Motherboard maybe?

I don't know but why would it be? It works fine via HDMI just not with DP so if it was a refresh or display mode then wouldn't that happen no matter the connection?
I have an AOC Q3277PQU monitor. No issues until now.

Okay, thank you. Yes they are the same. I swap to HDMI from DP and I don't hz to change the settings at all. In fact if I try to change the refresh rate from 59 to 60 hz nothing happens. It just stays at 59.

I returned the previous card and now have another and I have the exact same problem. This is crazy.
I contacted AOC, the monitor company and spoke to a helpful tec. He said it is an issue with the graphics card and I would need to speak to Nvidia. He said the problem is linked to the refresh rate and dropping it back to 59 HZ fixes the problem. Unfortunately my refresh rate is at 59 and I can't even make it use 60. When I select 60 it applies fine but as soon as I check it again it's back at 59.
Does anyone have any suggestions on what to do now?
I just uninstalled the video adapter and reinstalled the driver for the card as Microsoft suggest but that did nothing. I will contact Nvidia but I don't imagine I will get anything from them for ages.
Please help..

1) 59/60 Hz this is a non-issue, it usually just the software rounding up/down the display of numbers. The actual number maybe somewhere between 59 and 60 Hz for some displays.
The choice of 59/60 Hz does nothing.
https://support.microsoft.com/en-us/help/2006076/
But I'm not an expert AOC tech...

2) What exactly do you mean by flickering. That means different things to different people. A still photo or video would help.

Your further options are to use the Graphics Card at stock speeds (even if supplied OC) and try older drivers, as Nvidia issue these at a rate of knots no problem with that one.

Further tests would involve using another monitor with DisplayPort inputs. To eliminate a monitor fault.