Buy a dedicated box and you won't regret it....

I disagree with everyone's default statement that buy a new box. I have a bunch of customers on Epicstream who use Smart TV without many issues. Epicstream offers one of the highest bitrate videos out there and customers have no problem. So I won't always be quick to point fingers at the TV.

#1 First determine if the problem is with the feed or the App. Try the feed in VLC on a PC. If the buffering still occurs then you know that it was stream and not your TV. Your seller should have provided you a M3U8 link, copy and paste that in VLC. Watch a channel for 10-15 mins and see if the experience is different?

#2 If the buffering does not occur on the VLC, then yes you can point the finger to your TV or your wireless connection. If the buffering occurs on your VLC as well - its time to switch providers :) msg me if you are interested in Epicstream or check out /r/iptvreviews for other providers

While you will always get a smoother experience on a dedicated box on Dreamlink T1 or MAG 254, don't always be quick to point to the hardware, always check the stream and network :)

Good luck

Is your Sony smart tv android tv?

Sony runs Android so you can try lots of different ones

Got some STB and app video reviews over at /r/iptvgta in the sticky at the top. Might give you some good ideas.

Be sure to check out the popular dreamlink t1 review though if you really wanna step up your iptv game

Is it one of those Android tv's? Why not try Perfect player? Works well on the old fire stick I have and also on my S7 edge. Smart IPTV works well on my Samsung smart tv. On the Smart tv app, have you changed the buffer setting to 10?

Nvidia shield TV

Although, with the buffering. Try downloading arez wizard

Tweaks , advanced XML settings

Let it pick for you , restart Kodi and try again