This was very rare. It will be a brand new jury deciding the penalty so hopefully there will not be another mistrial!
The fact that it's so rare is what is concerning me. I found this link that speaks to the issue when there was a mistrial in the penalty phase in Texas. The defendant WON on appeal, but it was ultimately reversed by a higher court, The Court of Criminal Appeals then reversed it.
You can read about it here, it's not very long, a summary on a law blog: https://www.johntfloyd.com/new-rules-for-mistrials-at-punishment
I guarantee Temple's attorneys will come up with some argument.... and considering Temple's last appeal, which he should have lost, this makes me nervous.