Chromecast2 Buffering

[#1]

I am having problems with a new Chromecast 2 I am casting from an iPad2. I use it with BBC iplayer which buffers a lot. If I use the Ofcom wifi checker on the iPad next to the Chromecast  it says my Wifi is good, If I check my broadband speed with ookla on the ipad it reports 30-34Mbs. If I give up casting to the Chromecast and airplay to an apple tv in part of the house with less good wifi it works just fine no buffering.
If I check the wi0 stats on the routers expert page I see a lot of errors (errs) under transmitted. I am wondering if there are problems with the Chromecast 2 and the Plusnet supplied Sagemcom router. ( If my daughter airplays her music to an Apple Airport Express near the Chromrcast she gets no buffering, but there again music does not require the bandwidth of TV )

[#2]

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I see a lot of errors (errs) under transmitted

Errors on the transmitted wifi would suggest you've got interference of some description and it's having to re-transmit data... (if it is indeed lots)

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but there again music does not require the bandwidth of TV

Which I'd imagine is why she has no problem.
Do you have lots of wifi hotspots in the area? are many on the same channels? is your router near a 'heavy' power usage item (like an Air Conditioner, de-humidifier, Fridge, freezer etc.)

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less good wifi

Strength & Quality are very different beasts, you can have a great signal but poop quality. If you can look at the error stats whilst it's struggling to play, do you see the error counter count up rapidly?