If possible can you set up a Broadband Quality Monitor (BQM) at thinkbroadband.com - this will give you an insight into what is happening with the signal at the other side of the Hub, it will take a few hours to get any kind of trend showing although you should post the link straight away.
Please post a 'Live Link' to your BQM on here straight away.
Instructions for posting BQM Live Link
Under your BQM graph are two links in red.
Click the lower link (Share Live Graph) then click generate.
Copy the text in the Direct Link box, beware, there may be more text than you can see.
On here click the Link icon (2 links chain to the left of the camera icon)
In the URL box paste the link you copied and in the ‘text to display’ box write My BQM then click OK - you can post the link straight away.
Type 192.168.0.1 (192.168.100.1 in Modem mode) into your browser URL bar and press enter.
Hub 2 & 3 When the page appears DO NOT LOG IN but click ‘Check Router Status’.
Hub 4 When the page appears LOG IN then Advanced Settings > Tools > Network Status.
Copy and paste the contents of the Downstream, Upstream, Configuration and Network Log tabs onto here, if you get a yellow / straw box warning click the Post button again. Use one post for each tab if you wish.
What speeds do you get at >> SamKnows << with a direct connection using a Cat 5E or better ethernet cable between the Hub in Router Mode and a 1Gbs capable Pc/Mac/Chromebook and no other devices connected ?