At work we have a 2Degrees VDSL connection - Bridged with a DV130 and using an ER-X as the router.

Currently waiting on Chorus to sort out build for MDU so Fibre might still be a while away. 

Sync speed is around 55/11 and rock solid, and in the past we were able to max that out without issue. Recently we've been 'feeling' the internet is just not very snappy. Random long load times on pages, having to cancel and refresh pages to get them to load, and low downstream throughput - for example downloading the Win10 1903 update with the update assistant would always max the line speed out and be very solid, now the speed varies between 15 - 40mbps and is all over the show. 

Generally when a speedtest it run it will still get to 50mbps or so, but we're just not seeing that throughput most of the time in the real world, when we always used to. 

We have swapped the ER-X out with another but restored the config - unless there is something super weird with our ER-X config that's causing issues, it seems to be something external. 

For example, the below image is with a computer downloading the 1903 update with the update assistant. previously this would be rock solid at about 51 - 52mbps and the throughput graph on the Edgerouter would be flat at that speed. You can see there that it's all over the show. 

Any ideas on the best way to troubleshoot this? Thanks.