Chrome under sandboxie shows BORDER in win 10

[don0098]

windows 10, sandboxie 5.01.4, and lastest chrome.

under sandbox settings and appearance, "display border around the windows" is NOT checked. However, chrome still shows BLUE border maybe 2~3 pixels thick.

chrome not sandboxed doesn't show any border.

Is this a bug, or it's supposed to be like that?

thanks.