Some projects just don't work smoothly... even when you are accustomed to the machine, using the same batting, etc.
Try if there is a difference in stitch regulator on or off, likewise if it is one particular direction. You may have to clean the sensors and/or tracks.
I have one quilt that the stitch quality is just terrible on, it was an easy quilting pattern, I had done a quilt a week or so before that was fine. The one after was fine. But this one was not...
You've probably already done it but it can't hurt to change the needle again, sometimes they have flaws or the machine I used was very sensitive about it being perfectly aligned, of course it had nothing to really help you do that. I would take the old needle and stick it in the eye of the new needle to keep it aligned while tightening the screw.