Upload speeds dropped to 0.7mbs Help!

[Slakers]

Recently upgraded to BT Fibre2 and all was going well until last Sunday when suddenly the router started to cut out and our broadband speeds dropped considerably- particularly the upload speed which has gone from 10mbs to 0.7 mbs. I have reset the hub and pressed reset factory settings. BT have already posted me out a new smart hub 2 router and the problem persists.   We were having issues with the upload speeds before we upgarded to Fibre2 and BT sent an engineer to the property who looked at the wiring going into the property (a small grey box in garage) and he replaced the faceplate of the master socket which is in the living room to one which has an inbuilt filter (says Mk4 on the faceplate) - you plug in the broadband cable to the left side and the telephone cable to the port next to it on the right. Whatever it was he did, solved the issue and upload speeds went back to 9. 

I am now at a loss as to why this is happening again and why the upload speed has dropped back to 0.7mbs.  

[imjolly]

can you check the faceplate of master has not come loose as it only clips on and there are no screws - a small bump could knock it loose

[Slakers]

Thanks for replying - ive checked the clips on the faceplate and they are clipped in not loose