I have a Bernette 82 and it can be tempermental. It has to be threaded just right and you have to be very careful when winding the bobbin. I always test the stitches before I start sewing on a scrap piece of fabric.
The good thing about it is you can use standard needles and feet on the machine which saves you money.
Would I buy another one, probably not but it does the job onces you figure out its little issues.