VDSL half Speed on MikroTik

Dear all, i just have upgraded my ads line to VDSL and the strange thing is that when I’m using the Router/Modem from my provider the router ZXHN H168N it shows the sync at 49999 and it downloads with that speed, no comes the really strange thing when I’m using the ZXHN H168N as a modem in bridge mode it shows in its status 49999Mbps but when its connected to the MikroTik CRS125 it shows almost 19999


FYI

The upload speed its not been affected “WEIRD” its steady at 4999Mbps


Any ideas !!!


Where can i start looking.


Thanks again for everything.