Video exposure question

I shoot video with a Panasonic G2 and a Minolta MD 50/1.4 lens. I have run into a situation where the camera seems to overexpose to the point of blowing out the highlights. The interesting part is, when I set the shutter speed to 1/50 (by utilizing flicker reduction,) I get an underexposed image. All this shooting in a dimly lit room with aperture set at 1.4.

It seems strange to me that the camera would underexpose so much with shutter speed at 1/50 and overexpose in automatic mode. Does this mean that shutter speed is even longer than 1/50 in auto? I was afraid to close down aperture, thinking that the camera would have to boost ISO if I did that. What you see on the camera screen is not always the true representation of the image, as far as I understand.