The trick is not to rely on 1 speedtester only. On my multiple 330/50 lines, I've never seen more than 150 Mbps on the TBB tester. However nearly every Ookla server gives me around 310 Mbps on both single & multi thread tests. Real life downloads max at about 40 MB/s. Ditto on fast.com. So absolutely nothing to lose sleep over.
The fact that you're seeing 900 Mbps on fast.com (Netflix speedtester) may
mean there's nothing wrong.
What do the various Ookla (speedtest.net) servers give you? I would manually choose the Vodafone test server in London and Xilo's server in Maidenhead as they seem to be fairly accurate. Also try the AAISP tester as well
BT Business FTTP 330/50 -- Netgear RAX200
Edited by Highland76 (Wed 24-Jun-20 09:26:58)