I recently updated macOS to Sequoia 15.5 and got Xcode to 16.4. Live issues are now working again! I've been keeping up-to-date with macOS and Xcode since I posted this question and hadn't seen any change until now. I also recently did "brew update", "brew upgrade" and "pod update" in the terminal, but I doubt those are related.
Wish I could explain what exactly went wrong, but for now, it looks like getting updated resolves the issue:
Recommended steps: