This.
Another thing I've found is that even a well-tied knot will "slip" around the hook eye and burn the line. What I mean by that is that the knot sits on top of the hook eye when you tie it. After several casts, it will begin to slide around on the eye of the hook. To the side, back to the top, to the other side, etc. This is worse with a Texas rig because the weight right above the hook ensures that any fulcrum between the line and hook is right on the knot. I've actually found it to be worse when pegging the weight, which I think makes sense if you're following me on the fulcrum idea.
I always super-glue my knots for this reason - not to hold the knot together (though I think reinforcing the knot is another advantage), but to prevent it from sliding around on the hook eye. Once it does that, it's like cinching down a knot without wetting it. Snap! Another thing you might try is a loop knot (like the Rapala knot), though that creates an issue of more wear on the knot from the weight and also prevents the weight from sitting flush with the hook eye.
Last: Any chance your lake was infested with zebra mussels at around the same time this started? I remember them showing up in the Ohio River some years back and during the initial population boom, we experienced exactly the same thing. If you had a bite behind a stump or rock, you almost needed to steer the fish out before setting the hook. You'd break off almost every time. Zebra mussels usually have a massive population explosion when they first show up before the population stabilizes and becomes less of an issue for fishermen, at least from a breakoff perspective.