Why does my Z30 screen show a dark image of the virtual keyboard

This happens on all panes.

On the lower part of the screen the outline of the virtual keyboard background shows up black and the bar showing the phone, magnifying glass is flickering.

I first noticed this flickering a couple months ago while leaving it on charge overnight and up to last week, when I removed the charger cable this went away. Both chargers are Blackberry.

Also while typing, the virtual keyboard top row keys are displayed OK. The second row of keys is blank but by trial and error pressing the location of the keys does produce text on the screen and identifies the dots while entering passwords. The third row is legible but faint. The fourth row with the numbers, comma, space bar etc., is faint and legible, but the complete bar is flickering.

Answering calls, the bottom swipe to answer, or not bar is not legible, so swiping rapidly to the left sometimes answers the call.

Sometimes for no reason the screen goes back to normal. I have seen it go back to normal at 8AM and then at 9PM.

Try pressing the power button three times quickly,