Im new on the forum, having exactly the same issues as OP. Day 1 install of Fibre 900 FTTP , 921 dl / 50 up. After 2 hours upload speed increased to 95. Wi-Fi has been temperamental so spoke with tech support yesterday who reset my router and now back to a capped upload of 50.
please can somebody help me ..
There are other posts like yours and solution appears to just maintain connection and should correct itself in a couple of days if after 3 days no change then post back