ONE R 1-inch brightness gain

When I record in the house, and it loks good until I pan camera past the window with light coming in, then the camera seems to do some 'auto gain compensation' like my Canon camcorde, but I can't find a way to turn it off to get proper manual exposure like I can on Canon, so the brightness of the image gets corrected by the camera, but only at 4 frame intervals so the image brightness shifts around like it is doing auto-iso.

How can 1-inch mod be used to have manual exposure where the camera does not try to adjust the image brightness gain? The camera is unusable in this state.