Don't know anything about that workout, though I do know plenty of people struggle with back issues from diving into a jump routine that is too strenuous.
In my personal experience with back soreness and issues with fellow training partners, the problem is often (of course, not always) in the opposite glute. In your case, I would guess that your left glute is weak and/or lacking mobility. Check out any number of hip mobility routines and see if you are getting equal range of motion on each side. There are a lot out there, DeFranco's Agile 8 is a popular one.
If you do find this is an issue for you, I enjoy bridges and single leg deadlifts for strengthening the weak glute. Start with a few sets of 4-5 reps on the weak side and 2-3 reps on the strong side. Don't do this forever, but a few weeks can start to make a difference.