It's difficult to work out exactly why your speed went down or up again, the lfsg command show should if G.INP a.k.a. ReTx is currently in use. Unfortunately, the driver ChangeLog file mentions a bug about the lfsg command not displaying the ReTx status correctly (fixed in driver version 4.14.4). Also if G.INP was in use, the total ActualImpulseNoiseProtection value should be quite big, around 40.0 which would be displayed as 400 (it's given in units of 0.1).
As for your speedtest results - perhaps your ISP has a copy of the IP profile number, which should update automatically, eventually.