wow, that's really impressive! check this Threads video - it is basic but contains some useful tricks. Also, have you tried interfacing with a fusible, or with silk organza. If you test, test on a scrap with interfacing. You may try not to obstruct the machine, that is don't pull or hold the fabric too much? What else, have you checked if a regular zigzag works well on your machine - it seems to me there is a problem with the lower or upper tension, what kind of fabric is this? but this is something that you may resolve with the help of interfacing. But, in any case, don't dispair - I had so many issues with buttonholes. I must say, since I switched to my simple Bernina I have never had to fine tune anything.
oh, and I forgot to post a link to the Threads video http://www.youtube.com/watch?v=9erxiBoAwpg
In some of them it looks like you or the machine are moving the fabric too much for each stitch. Mine works best if I just let the machine do it, (with a little bit of guidance to make sure it doesn't try free motion embroidery or something) but then mine is a fantastic button hole machine.
@ Marina - thanks for the link, that was good to see! This was the first buttonhole run on my Emerald Viking and so I was a bit surprised to see that it had what looked like (to me) tension issues on the recommended settings. And I couldn't find anything online when it came to automatic buttonhole tension issues! A friend played around with it since then and was able to get an acceptable buttonhole, but it seems very temperamental. I'm pretty surprised given the Emerald reputation! What Bernina do you have?@Naomi - I'm happy to say that each of those buttonholes was completely hands off by me. It seems to perform the function ok, but the thread/tension issues were, as I said before, pretty surprising given the make of the machine. I'll keep practicing though, especially if yours doesn't have issues!