Laptop plays streaming video, Firestick doesn't ...

[opn2020]

I have been attempting to get a split tunnel VPN working. One machine on the network goes through the VPN, all the others don't. My config seems to work - one machine gets routed through the VPN the rest don't. But there's one major problem, my Amazon Firestick connects to the Internet fine but gets a "spinning wheel"/buffering if it tries to play streaming video(from YouTube/BBC iplayer/Prime video etc - the apps load movie thumbnails fine but won't play streaming video). A Windows 10 laptop connected to the same WiFi access point as the Firestick plays YouTube and BBC iplayer with no problems - the issue appears to be Firestick(Android?) specific. Basically everything seems to work apart from streaming video on the Firestick.

Any ideas why I have this issue?

[opn2020]

Making some progress ... turning off IPv6 has allowed YouTube and Amazon Prime video to work on the Firestick. BBC iplayer and other UK TV streaming services will load but still won't stream on the Firestick, not sure why unless it's related to IPv6 in some way?

EDIT:

Somehow managed to mess everything up, so reset to defaults - and then YouTube wouldn't work on any host under default settings. Turned off IPv6 again, set MSS to 1472(PPPoE connection) and YouTube started working, then set up my OpenVPN client again - finally everything seems to work as it should as far as split tunnelling goes.