Okay, first thing I'd try is the demo mode. If you're still having the same issues there, then yeah, it's definitely a bug.
Then, if it looks like it's recording (that green bar is moving) and the app's still responsive (buttons work), then it's probably a network issue. In that situation, just wait for a bit – maybe a minute after sending your prompt – and don't do anything.
Otherwise, if the app feels totally frozen or just isn't responding, then there's not much you can do, and that's on me. I might consider dropping it on Steam, and if I do, I'll refactor the code and keep this in mind.