getCharBoundaries returns incorrect values when TextField or parent is rotated in 3D

Everything is in the title:

I'm just trying to make a sprite follow the last letter of a TextField with the getCharBoundaries() function. It works fine when the DisplayObject that contains the TextField has no 3d transformations on it. But when I rotate it in 3D, returned values are wrong and it doesn't work anymore.

I don't know anything about the matrix objects and all those transformation functions but I guess there is a way to get the correct value by using one of those matrices.

I tried to use some matrices and played with some of their values but didn't get any luck.
If someone knows anything about this issue, let me know.

tkx !