I've recently had BT full fibre installed into my property and am having a strange problem in that whenever I start to upload anything my download speed completely drops and becomes unusable.
I'm on the Fibre 1 package and usually get 50Mbps down and 10Mbps up, but as soon as I start to upload to file to cloud storage or transfer something from my machine to another over a VPN the download drops to around 5Mbps and will stay there until the upload finishes. If I kill the upload the download speed will instantly return to normal so this is definitely the cause as far as I can tell.
I'm using a different router (Ubiquiti edgerouter) and am measuring the speed from there, and have also run speed tests from multiple devices, both wired and wireless. I have also used this edgerouter on 2 different connections in the past and only started having issues when moving over to the full fibre connection so I don't think this is where the problem lies.
Does anyone have any suggestions as when I tried to contact BT support they were less than helpful...