[williamting]

This is actually not a bug. It occurs when you did not correctly position all the lips inner outlines when the mouth is open. When the mouth is close and if you did not merge the inner two outlines, you will get a strange mark also. In the example given, it appears you did not position the bottom left and right marker accurately. To resolve this issue, you can merge the inner lip outlines by dragging them to meet each other or readjust the outlines. Use the interactive screen to do the adjustment (this is done by switching on the Before and After View. Move the mouse over to the "Before View" and adjust from there.

You get the same issue (orange mark) when the eyes are not wide open. This is especially a problem for people with smaller eyes. For eyes, you just adjust the eyeball outline smaller (or to the minimum) or switch off eye control.

Wish you luck.