Just like a paper clip, after something is bent and straightened enough times it will begin to weaken. And eventually break.

Check the tiller and see if it's still tillered out right. String should be between 1/8 - 1/4" closer at the end of the bottom fadeout than the top for split finger release. If it's out of whack, start checking the glue lines real close for signs of delamination.

With the bow strung, stand back and look at the curve of the limbs. Look for an abnormal hump or flat spot along the limb contour of one limb that doesn't show up on the other limb. If you see such a spot, that's a good indication she's about to blow.

Oh, and be sure to check your new scale against a couple of others. Sometimes scales aren't calibrated right.