HI. With the computer wired connected, and when installing programs on Steam or downloading big files at high speed (maybe more than 300Mbps), the WAN connection is lost for some time and then later resets and start working again. It is like a buffer is full or the processor hangs until reboots.

Cables are cat 6 and the port is at 1Gbps. As far as I know this behaviour is not shown when connecting using Wifi.