Thanks for the replies. I never use the camera in aperture priority but all shutter speeds work fine the manual and electronic ones. Hence I assume it is something to do with the metering system. The main circuit board and all the electronics have been replaced/checked. When the problem occurs, the led lights for either over or under exposure, top or bottom of the scale and stays there, regardless of shutter speed change, aperture change or ISO change. Usually, if another exposure is made it will then go back to giving a correct reading. Yes, double exposing the frame with a cap on would perhaps be a good way to avoid wasting shots. Usually if I am lucky the light value has remained the same and as I am on manual, it does not matter too much.