Since that is the back of the quilt, it looks as if the upper tension is not tight enough. If you have some *unwaxed* dental floss, try flossing between the tension discs in your upper tension. A bit of lint caught in there can cause this type of problem.
First, though, just try tightening the upper tension by 2 numbers or so and see what happens. It may be that oiling changed the tensioning requirements.