Two 'a' contours on top of each other?
Have you ran the FDK's CheckOutlines on your font?

Thanks! It wasn’t a double counter, but for some dumb reason I had pasted in the original a contours and not deleted the component in Fontlab.

That is the same as two contours, James. We have all done it :-)

ChrisL

The way I check for this is to do control/command (PC/MAC) - click near an outline. That chooses the outline, lighting it up in red. If there's a second identical contour in black over it, you'll see a little red around the black, rather than a clean red outline. Then you can just delete the extra outline.

The Font Window can also give you a clue that something is wrong with the glyph as the preview appears a little bolder and less smooth.