My first new muzzleloader, a T/C renegade .54, had a very similar issue. Since I bought it from a buddy, my first question went to him. He took it for a week or so, gave it back and, though tight, was no longer a rod breaker. I asked what he did, he replied "I shot the h*ll out of it!"
(He may also have given me back .10 vs .15 patches)
I also just solved the opposite issue(waaay to easy to load) by switching from swaged to, I assume, cast balls.
So, unless you feel it's dangerous to do so, it may helpful to shoot another ball/patch combo...often.