Missing vertical lines on LCD (TM12864L-1 model)

Hi all
My LCD suddenly doesn’t display several vertical lines and the missing lines are changing at different locations after each time it is power on. Please see the pictures attached. I haven’t used it for a year or so.

The LCD is TM12864L-1 model, made by TGK and I run it on the Mega2560.

Would it be the voltage or current problem ?

Tony

TM12864L-1-TGK-manual.pdf (83.6 KB)