Cut-out problems generally stem from either an edge problem or a blending problem. Edge problems can often be fixed by adjusting the Edge Finding options, while blending problems can be fixed by adjusting the Edge Blending options or touching up the blend masks.
Note: In both cases, you can either create a patch to use localized settings for the problem area or you can apply the setting changes to the whole image (applying changes to a patch is usually much faster).
To fix edge problems:
If color contrast across a missing edge is low, adjust the Edge Threshold lower and the Number of Objects setting higher.
If this doesn't work, set the advanced Edge Contrast setting to low with the Edge Finding options.
If the edge still isn’t found, you can draw an edge manually using the Forced Edge tool. (See Forced Edge Tool.)
To fix blending problems:
Make sure the blend mask starts at a dominant foreground color and ends at a dominant background color.
If the blend is too noisy, adjust the Intelligent Blending setting toward Feather. You can also use a very thin blend mask.
If background colors aren’t being removed, adjust the Intelligent Blending setting toward Smart on the Edge Blending palette.
If contrast is low across the edge you may have to use a very thin blend mask or feather the blend.
Use a patch for the area and use the Complex - Hair options on the Patch Properties Edge Blending tab.
To learn more about how blend masks work, see Understanding Blend Masks.