Yeah, cable quality is always an issue, and even when certified or using a name brand known to work there can be issues. I've probably got at least a dozen different brands in the house. I was lucky enough to find a deal and took a chance on a pair of HDMI 2.1 cables when I got my LG C2 but I had other cables, including one Monster, that didn't fully work for the PC but do still cut it for the 4K disc player. From DP to HDMI, I can't recall how many times I've run into an issue that ended up being cable related. The shorter runs are usually easier but anything over 6 feet tends to become a gamble but eventually I've been able to find something. Back track though, 80 Gbps, we're flying now folks!