Xbox one S only getting 6mbps over wifi with CS9000 YouFibre sage com router

Has anyone else experienced this?

I have recently got YouFibre 900 which came with a sagecom cs9000 router. long story short, I'm getting great speed on nearly all my devices however with the xbox one S I've only ever managed to get around 6-10mbps over wifi with this router. (with previous ISP (BT with smart hub 2) getting over 200mbps)
I've tried many different things including port forwarding, connecting the xbox to the legacy band (I understand it's an older device), turning of ATF and APSD, disabling IPV6 and even resetting xbox network settings to no avail.

I've tried it using an RJ45 into the router and getting 300mbps there
I've tried the console on wifi over a friends house running a smart hub 2 once again as per usual 100+mbps (they were on a copper line at that point)

has anyone else had this issue, and if so how did you fix it?