All streams suddenly dark, pixelated and generally unwatchable

I use Netflix, Prime and Plex extensively and have been happy with the Roku (Hisense 50") for a good year now.

Yesterday after watching some Netflix the TV was turned off and then back on about an hour later, nothing happened in-between.

On turning back on again all the streams, Plex, Netflix and Prime were dark, grainy and unwatchable.

Moved from wifi onto ethernet and tested: 200mbit download so no issues there.

Reset all tv settings, no joy.

Eventually i factory defaulted everything and when it came back up it started working again.

Anyone else had this? Or have a better fix than defaulting the TV?

TIA