Slow or next to no connectivity when USB tethering

Hi,

I'm a bit stumped as to what my problem is, but I've followed the rndis configuration guide for Smartphone USB tethering however, I can get connectivity to the outside world (e.g. run ping tests) but when I do a ping test I end up with < 0.05Mb! Going via speedtest.net I do see the speed start for at 5Mb (for a millisecond) then it seems to go under 0.05Mb, it feels like there is some sort of throttling going on(?).

I get the expected kernel logs...

[ 1785.418904] usb 1-1: new high-speed USB device number 2 using dwc2
[ 1794.263116] usb 1-1: USB disconnect, device number 2
[ 1794.842905] usb 1-1: new high-speed USB device number 3 using dwc2
[ 1795.062761] rndis_host 1-1:1.0 usb0: register 'rndis_host' at usb-1e101000.usb-1, RNDIS device, 6e:c8:49:25:89:d8

When I plug in the phone via USB directly to my windows laptop I seem to get a decent speed (approx 25Mb)

I'm using a plusnet one hub and a galaxy s10 via Three.

thanks!
Dave

just an update to this, ive just tried a s9 on three (via ID mobile) and I get decent speeds! so I think its the phone? maybe driver?