No such issues on my black AT&T Lumia 1020. Sounds really weird, can't think of why it would cause a crash?
Then again, I've noticed using WordFlow for extended periods of time can make my phone really warm, and can hit the battery pretty hard. I'm still not sure if it's the apps I'm using while typing or WordFlow itself, but I'm becoming very suspicious of how much processing power WordFlow requires.
While unlikely, it does seem remotely possible the processing required to decipher your swipes is too much, causing the phone to crash. Unlikely, but at least worth considering. I'm still investigating, as I doubt it requires /that/ much power, but my battery seems to go down dramatically when I'm using it.
Hope that's not the case, as I really love the feature, but I'm willing to sacrifice the convenience in favor of battery preservation.