I have 2 CPE510 devices. They are connected over ethernet to a TP-Link Deco M5 mesh router. Its not connected to the main deco its connected to one of the others. When I start a download over the CPE510 the speed will start out at a few MB/s for 5 or 6 seconds. Then the speed will drop to around 100KB/s. I tried walking over to were I could connect dorectly to the Deco Mesh network and it would stak at several MB/s for the whole download. 

What can I do to resove this. It seems like shorter transfers are ok so things like web browsing seem ok but any file download will crash to these ulta low speeds.