Thank you but problem solved already.
to fix buffering on android tv use this and save it in your user data:
advancedsettings.xml
xml:
<advancedsettings>
<cache>
<buffermode>1</buffermode>
<memorysize>209715200</memorysize>
<readfactor>50</readfactor>
</cache>
</advancedsettings>
I have specified 200mb buffer above, but that translates to 75mb inside kodi - do not know why that is. Kodi wiki notes that specifying 100mb will use 3 times more memory in the system (300mb), but I guess that info is outdated as specifying 200mb allocates 3 times smaller buffer in the app.
Heres is my keymap file:
gen.xml
xml:
<keymap><global><keyboard><key id="61667">activatewindow(home)</key><key id="61668">displayinfo</key></keyboard></global><fullscreenvideo><keyboard><key id="61670">playerdebug</key><key id="61669">playerprocessinfo</key><key id="61668">displayinfo</key></keyboard></fullscreenvideo></keymap>
The above keymap adds displayinfo(yellow) and playerprocessinfo(blue) to the color buttons. Also Home (red) and Videos (green).
With the above settings UHD 4k content above 100mbps with Kodi 18 beta 5 is smooth on Sony TV X85 series.