Sounds like your Juki is a bit tempermental - I have one of their straight stitch machines which usually runs like a champ. Once in awhile it's a bit picky but usually it's one of the few things you mentioned. I wonder if what you were sewing at the time might not have worked well with your set-up? Or, it was just the Juki Gremlins at work! Glad you're back to smooth sailing!