The woofer's voice coil can create a problem in rare cases, in the form of back EMF. I've seen woofers "chirp" piezo tweeters from back-EMF, but most woofers don't do that.
That's interesting. They weren't chirping though, so that's not it. I've only had two instances of burning the resistors internally mounted in the drivers. But it only happened twice and never happened again.