After some problems with 4K panels its obvious that many DisplayPort and HDMI cables that work at HDTV resolutions do not work so well at 4K.
HDMI 2.0 and DisplayPort 1.2 are both capable of handling 3840×2160 at 60 Hz with standard 8-bit color. 10-bit color requires 25% more bandwidth and that can pressure HDMI bandwidth.
Many cheap cables lack adequate shielding to protect the signal from degradation. Other problems such as smaller wires can also adversely affect the performance.
Old HDMI seem to work better than DisplayPort cables on my experience. This is surprising given that DisplayPort has generally been more demanding than HDMI in the professional display market.
Heavier cables with more shielding seem to work best. These cost more due to the additional weight but apparently this is a cost that has to be born. Check with the vendor to be sure the HDMI cable is 8K ready which will represent the best quality cable. High quality cables are more expansive but worth it for the best image quality.