Thanks for the update!
The `do` command following a title is still broken in the new version and this example. Same thing happens, soft lock after dialogue briefly appears and disappears. I never got back to this post before but if I remember correctly, it's a timing issue and the state getting messed up. That was 2.44.0 though, so it might be different in 3.0.0.
edit: I found some more of my comments in a Discord on the timing issue. Specifically, it's in the _on_mutated() function and the timer that always hides the balloon after 0.1 seconds that a `do` triggers.