I just released BandHelper 2.1.18, which fixes a crash when navigating through the app menus in Android 8.
I'm aware of another problem where time and duration pickers don't save their values, but I don't have a fix for that yet. I'll update this thread when I do.
Feel free to share your experiences with Android 8 here.
The time and duration pickers were fixed in app version 2.2.