works fine in most situations, but if the scene changes brightness, the exposure is adjusted.

Note that this clip starts out fine. When the door is opened, the camera adjusts to the bright background. This leaves the foreground (inside) too dark.

Contrast is the difference between light and dark. When the contrast ratio (light area compared to dark area) becomes too great, something has to suffer. You can adjust the exposure manually and make the indoors look correct. Or, you can adjust it to make the make the outdoors look correct. To make both areas look correct, you would have to add light to the indoors or block light from the outdoors.