K850i keys causing bright flashing of screen

Posted by alps
My K850i screen shines extremely bright at times when I press the down/left cursor button and some other lower buttons. It happens intermittently and seems to be most noticable immediately after fully charging. Sometimes however I can't replicate the problem.

I may have spilled some water on it around 6 months ago. Other than this the phone functions ok. The bright flashing is almost as though there is a short-circuit letting too much power through to the back-light. It is so bright that it hurts my eyes when it happens suddenly during writing a text or something. It is very, very annoying.

Please could anyone advise on how to fix this problem I would be most grateful indeed.

Thanks,
Andrew