I'm having the same issue using the Celtic Knots Inverse font with Designer 3.102 and Centerline fonts. Get little plus signs between the characters like the first image in this thread. I tried it in 1.187 and got rid of the plus signs. But even with 1.187, I'm getting little pyramids (as indicated by red arrow in image) between the characters if I use the 60° bit. The 90° bit gets rid of the pyramids, but I otherwise prefer the looks of the 60°.
I emailed Clanbadge (maker of the font) to see if they have a newer version - no reply yet.