I have a FolgerTech Kossel 2020 that uses the typical MEGA2564/RAMPS 1.4 board combo and a ReprapDiscount graphics controller. For a year it has been just fine, then suddenly the display scrambles about 10 minutes into a print. A reset brings it back, but it always scrambles now. I got another one, and it does the same thing.


Does anyone know what causes this? How to fix it? Is something overheating on my main board?

Many thanks,
DLC

Normally electrical interference

Move cables going to lcd as far as possible from any other cables. especially hotend, heated bed and stepper cables.
If you cant move them try shielding them... wrap lcd cable with aluminium foil or use real shielded cables

Also check all you ground connections are solid on power supply's and control boards.

I had and solved this problem.

I have an aluminum frame 3D Printer and routed the LCD cables alone the T-Slot covering them with Aluminum Foil Duct tape from my local Hardware store.
First I found the route that gave me the least amount of interference, Which was at the front of the printer. Then I ran both cables alone the T-Slot.
Placing each cable on a different side of the T-Slot and covering them with a 20mm strip Aluminum Foil Duct tape the length of the run along the T-Slot.
One run being on the bottom side the other hidden on inside of the frame, An have not experienced any LCD corruption sense the fix.

I did not do the following, But you could even spray paint the Aluminum Foil Duct tape on the exposed outside edge before covering the cable to blend it with the color of your printer.
Covering the cables with with blue painters tape first would make for easier removal of Aluminum Foil Duct tape if needed.