I have my paternal grandmother's 1959 Bel-Air portable zig zag machine. I am going to have to figure out what is "off", something with the tension. If I recall correctly it was a Japanese copy of a Singer model. MY mom and grandmother bought one each. My Mom traded her's in on a Singer Golden Touch n' Sew in 1970 or so, you could only buy it with a table, and the machine could swing away for storage, it's claim to fame was automatic buttonholes, also had some interchangeable cams for decorative stitching.
She really regretted trading in the Bel-Air.
I have now a Pfaff 545 H3, the big bobbin model, a true workhorse. Straight stitch only though.