RE: Dell Inspiron 7567 UHD model problem with 4K Video on Youtube
I will venture the problem is the bandwidth of your network connection - not the system itself. If you're absolutely positive no one is on the network at the same time AND your TV/DVR is powered off, 30 Mbps will feed one network 4K stream. As soon as you turn on a TV, use the DVR, or someone else signs on to the network, you won't have enough bandwidth for a 4K stream.
You may also want to test your actual network speed (www.speedtest.net is one way). You may very easily find that what you think is 30 megabit is really in the upper teens to low 20s (unlike fiber/DSL connections, cable connections are shared bandwidth - the speed will come and go depending on just what other subscribers on the same network branch are doing).