Hi all -- with the latest update, we have fixed the AI pitcher substitution bug, so they are now picking their relievers as expected, and will no longer lock up your game trying to pick a pitcher who's unavailable.
Thanks so much for your patience while we sorted out this issue. There are still a couple known crash bugs, but this pitcher substitution bug was by far the most prevalent. Please swing away, and continue to let us know if you have any questions or issues!