Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
I suspect that the meter may be defective; or the control circuitry of the camera may be misreading the meter; or, doubtfully, the control of lens aperture may be defective.
For that last, take a look at the iris in the lens (if you can, and if it has one... both, I doubt.)
It is possible that a rare setting is 'wrong' in a way that produces this behavior, though frankly I doubt it. Would you like to try a factory settings reset? which would wipe out all settings individual to you, and all configurations also... but might doubtfully help with the problem.
If so, let me know, and I will research instructions on how to do so.
How old is the camera? in months or years since you bought it.
Has the camera been dropped or otherwise subjected to mechanical shock(s) in its lifetime?
Has the camera been operated in or subjected to, temperatures below 32 degrees F (freezing point) or above about 100 degrees F ?
Has it ever been subjected to a humidity higher than 85 % or gotten wet ?
Has the camera been operated in a gritty or sandy environment, such as a beach, a seaside, a construction site, or the like?