Streaming audio and stability

now that I have full speed and with or without QoS the issue is

speed test 300/200 mbit test directly to fiber nod

speed test via router the same and I thought all is well bu NOOOOOO

i go to shoutcast via lan and streaming audio hacks and stops at intervalls

this is at top floor and from router there is a cat6 cable in to a giga 8 port switch and there is the computer

streaming audi hacks, web pages stops loading like interference 

I f I stream via WiFi all works

The router is factory reset but something is wrong

if I use web without xr700 all I super fast not hickups 

I connect via router port to switch and 30m cat 6 and all as hickup 

where the H shall I start in router settings

i have disabled QoS and all has 800/800 in speed settings