I've never known my bp to burrow either, then again my substrate is only a half inch deep at the most. But mine does push the substrate around, not sure why, the top of the bedding is 92 to 93 at the most and the glass is maybe a half degree higher at any time. Dimmer switches are not reliable at all you need to get a good heat mat regulator, I bought the hydrofarm one off amazon and it works fantastically for me. it in combo with my heat light keeps the temps right where they need to be. so I would suggest getting a heat mat regulator ASAP