Internet speed dropped from 800 MBps -900 MBps to half recently in Woluwe Saint Pierre

Hello,

I have since one or two years the 1 Gbps pack and the speed, tested at the router  on cable, was approximately 800 Mbps, so very close to the advertised one.

Recently I have seen that I barely reach 400 Mbps.

Any idea ? Thanks!

I am leaving in Bruxelles, Woluwe Saint Pierre close to Stockel.

Best regards