janeite, I agree with Joe Miller, from what I've read you can't get the cam stack "out of time." And that you may need to shorten, or tighten, your stitches to make them look right.
There is one other place to oil that I don't think has been mentioned and I wish I had a photo to show it to you, but I'll try to describe it. If you open the left-side door and look in at the needle bar, there is a round-ish thing to the right of the needle bar (as you look at it from the front of the machine). It's called the plunger and it goes in and out as the needle bar swings right and left when doing zigzag stitches. Oil it and see if that helps.