4k TV to Android TV Box settings

Hi,
After having a small success myself last night setting my 4kTV up to my box and quality been good on 1080p @ 60fps I have had a few wobbles today of very slow picture and juddering. Does anyone know if moving to 720 would be better or are their any other settings i can adjust to make my box run smooth. New to this. Any help much appreciated.

Thank you
Karlrog