Apple watch 3 full green screen

I’ve seen tons of threads on apple watch full green screen - these seem to occur once warranty expires. For all the posts and replies I can’t find a solution other than to buy a new one. My apple care and warranty have expired. Approved service centre says they can’t repair Apple products. Does anyone know of a solution? I’ve tried both hard reset and unpairing with phone but no success. The watch is still working its just since last charge the screen is solid green. Failing a solution does anyone know why it occurs so I can stop it happening with my next watch? It is only 2 years old and is my second Apple Watch -never had any issues with either previously.