Well, I tried lowering the tension to the absolute lowest, and I increased the length of the stitch a bit. I also stopped using heavy weight quilting thread and went to all purpose. I'm still getting the same issue. I've got some pictures to see if it gives anyone any ideas. It's really frustrating me.
Here's the front of the stitch:
And then, I flip the work and it looks like this!
Anymore ideas? It's a Brother LS-1217