Try turning Smart Steering off if you have it on. It might be the devices flip-flopping between the 2.4 and 5 GHz WiFi. With Smart Steering off it forces the devices to stay on whatever WiFi you set it up on.
To turn off Smart Steering - do this:
1. Make sure you are on the Telus wifi on your laptop/ipad.
2. After connecting to the router, open a browser and go to: http://192.168.1.254
3. Login with the user ID that's on the label on the T3200 Router (and not the extender). This will be different than your wireless access code.
4. click on "Wireless Setup"
5. Disable Smart Steering and try again
Btw, i had similar issue with my original generation Chromecast as well. I never did disable Smart Steering as I didn't know about the option back then.
I solved it in two ways:
1. I hard wired the Chromecast. Bought the Chromecast Ethernet Cable on Amazon ("Cable Matters Fire Stick Ethernet Adapter") for 20 dollars. All streaming problems on Chromecast went away.
2. I was still having Wifi issues in general and got a Google Nest Wifi to bypass the T3200 modem. The Google nest was fine for Chromecast, but now you have two separate networks.
I have this issue on the wi-fi hub. I've never seen a solution for it on here. I just deal with intermittent chromecast connectivity. It sucks.
People always suggest changing settings like disabling band-steering which work on older routers they have but that as far as I can tell (with chats with TELUS) you can't do with the wi-fi hub.
Other solutions such as hard wiring I guess work but don't really count as fixes to me.
The wi-fi hub does have a passthrough option which means that you could use your own better router, but you would need to theoretically hard wire your optic TVs first and telus wasn't able to confirm that hardwired optics to the router in its passthrough mode would work. I don't think they have (or had).