Lower-right part is missing on screenshot

Sometimes when I do screenshot of some element it's cut in the lower-right  corner. What can be a possible cause?
What element looks like (with some space around)
![expected space around](https://cloud.githubusercontent.com/assets/9070440/18310862/4348ccf8-7501-11e6-9bac-2740c795fdb9.png)

What I got on screenshot
![actual](https://cloud.githubusercontent.com/assets/9070440/18310857/3b22b43a-7501-11e6-92ac-9d132dcc6734.png)


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Lower-right part is missing on screenshot #48

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Lower-right part is missing on screenshot #48

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