Have just bought a sewing machine and will admitt that it has been years since I have used one but so far setting it up etc has been ok.
I have been trying out some of the stitches and when i try and do zigzag stitch (follwoing the settings suggested) i get a zig zag and then some straight stitches and then a zig zag. It's not in any particular pattern just really random.
Have tried adjsting the tension etc but it is still doing it.
I know this sounds stupid, but are you actually using blind hemming stitch rather than zig zag as this does a zigzag followed by about 3/4 running stitches. The graphic on my machine is very similar to a zigzag and I have picked the wrong stitch before.