I'm having an issue with my Xe75Pro and it's been like this for a long time. I have symmetrical speeds, so both should be just over 1gbps, however the download speed is the one that's falling short. The upload is fine. 

I tried a software update and even setting up the deco from scratch with only my phone, one device, connected and I got the same results, so it's not too many devices on the network. 

However if I plug a laptop into the modem and run a speed test, to bypass the deco, I get the full 1x1gbps. So for some reason the deco is holding back like 300mbps. I even switched out the deco to try another with the same result.