I also face the same scenario where the view finder is very dark when the camera app is opened , but its easily fixable by changing only the ev values once. maybe at start-up Cam-UI might be ignoring the reported correct EV values by the driver or whtevr.

Also changing of ISO and EV values at the same time never worked for me (resulted in too dark or none responsive ISO /EV settings which forced me to restart the cam UI), but behaved as expected if you change only one of the parameters from the either.

nkirk