I just plugged my new RAMPS 1.6 with it's LCD into my Anet A8 stock psu, and this happens... I don't think it's interference because the cables are far from any other
Marlin Firmware – How to install it to your 3D printer (Anet A8, Ender 3) – Crosslink
How to make the Marlin menus more responsive on Anet A8 - YouTube