Feeding fabric in machine - ends up curved
I have a Necchi Ex60 that is about 2 mos old. I was at class the other night and noticed that when I sewed narrower, longer pieces together (2.5in x 42in), and held it up, the pieces curved (towards the right). Last night, I fed in some fabric and let the machine pull it by itself. It would start off straight but inevitably would always curve to the right. I tried messing with the presser foot tension but that didn't seem to help.
Does anyone have any ideas? Is this common or should I take it to the shop?