Unbearably slow connection and ATOM errors

I'm on a new VM M500 package since July this year, which came with a hub replacement as completely new contract. The speed on both wired and wireless devices has been somewhat underwhelming, I've always run the VM hubs in modem mode with my own router and this one was no different but the speed and constant drop outs when running on my tp-link deco was unbearable and have reverted the dreaded SH3 to router mode for the last 2 weeks but nothing has changed, its managed to somehow get worse. 

Multiple pinhole & factory resets don't seem to be doing the trick, and while I did receive an email from VM last week to say they've noticed something isn't right with the connection and that a remote fix will be applied, with an email the next day saying its been fixed, it has improved nothing bar my BQM graph looking slightly less yellow. 

I've seen a few of the apparently dreaded ATOM self healing restarts in the logs which coincide with all connected devices not having an internet connection, but being connected to wifi and needing the network to be forgotten and then re-added to restore the connection.

All cables and connections have been checked multiple times, including using different cables and nothing has changed. Any idea what the logical steps here can be to get this working as it should? Engineer visit? replacement hub? 

Hub logs and stats: