flash as3: textfield borders disappear when drop shadow is applied

Question

Hi there!

There's a really strange bug I've ran into today. I have some textfields generated from code, and if I apply a drop shadow filter on them, sometimes the right or the bottom part of the textfields' border just disappear.

_passwordField.filters = [new DropShadowFilter(1, 45, 0, .75, 3, 3, 1, BitmapFilterQuality.HIGH)];

this is the line of code, which is responsible for this bug (is it a bug?) because if I comment it out, the borders render correctly.

here, I've made a little screenshot to show you how does it look like

the upper field has the drop shadow (and the right border is not showing up), while the lower one has no filters assigned, and looks like it should.

any ideas about what is happening here? thanks in advance!