202A Display faded on one side

I have just deployed a 202A display and it worked perfectly for about 12 hours, after which the characters on the left side of the display are faded, and the remainder are flickering. I can improve the situation by pushing the voltage up from 5V a little. It looks like the LCD is broken, but what could cause this type of failure? Obviously I don't want to fit another display and have it fail the same way.