Does anyone else have issues with our local TV on demand apps on the new(ish) chromecast with google tv?

I have read these devices do have wifi issues, and willing to buy a wired ethernet adapter if this will help but not entirely sure if this is the problem.

Netflix runs just fine streaming FHD with Atmos audio so this would be far using more data throughput I would've thought.

3Now, generally if your lucky you can get one episode of something then get plagued by "There was a problem playing this video" and have to restart the app, but usually it will keep doing it all the time once it does it the first time. TVNZ+ is much the same, constant problem loading video messages but you can literally hear the video still playing fine behind the error even if left for a while, clicking the button just results in the message just appearing again.  Both of these sometimes lead to the Chromecase dropping the wifi altogether or trying to switch to the 2.4ghz network.

This is where I am confused if its an app issue since Netflix runs fine, or a chromecast wifi issue that could be fixed with an ethernet adapter, or a router issue. But don't want to go replacing things to no avail haha.

For what its worth, I know the 3Now streaming can be quite buggy anyway, but generally behaves on a PC, but I dont want to watch it on a PC. Wired and wireless connections via PC seem to behave fine, desktop will download from game servers at good speed, and Xbox cloud gaming runs perfect on both. Router is an oldish Netgear Nighthawk D7000 so maybe due for replacing

If anyone can offer any insight if they've had similar issues would be much appreciated :)