Unreliable Hub Two Wifi with chromecast

[#1]

Since getting my Fibre 900 connection with Hub Two, I've had multiple problems getting a reliable WiFi connection to any chromecast devices.
They all disconnect/reconnect at random disrupting anything I'm trying to stream to the chromecast (I have 3 in total, all different non ultra versions of the chromecast).
Sometimes the connections will barely last a minute, other times if I'm very lucky 5 minutes.
I'm mostly concerned with streaming from VLC on my PC to the chromecast. The PC is connected via ethernet to the Hub Two and the chromecast is barely 5ft away from the router.
I used to do exactly the same connection via my "old" Hub One (and previous routers) with my 80mbit connection with no problem at all for years.
I've tried shifting wifi channels, changing the WiFi "mode" to possibly make it more compatible and disabling 2.4/5GHz radios.
But anything I try makes no difference.
Using the chromecast to stream from YouTube does work a bit better (because YT buffers and handles unreliable connections better) but still is flakier than with the Hub one ever was.

[#2]

Moderators Note

This topic has been moved from Full Fibre to My Router

[#3]

Hi @PT206 Thank you for getting in touch with us, I tried calling you however, I could only leave a voicemail.

I was calling to do an intrusive test of the line and carry out further checks, as I was unable to speak with you directly, I would request you to make contact with us on 03301239123 so that we can see what is causing this issue for you.