The Ready State Virtual Mobility Coach is like having a virtual Kelly Starrett in your pocket.
i suspected it was some kind of posterior chain activity that set it off. i’m not sure how your DL form looks, but it is possible you have glute inhibition on the right side. if you do, then hip hinging activities will cause you to overwork the hamstrings and low back when the glute is not firing properly. in this case, your low back is firing up to compensate for lack of glute activation.