I just purchased the Halion 5.1 (as an update from Halion 4). After playing with it for like an hour, especially with the Granular engine, I got a weird bug: after i duplicated the only layer I had in the program structure, I noticed that no matter what parameter I was changing it had no effect on the sound. Even when I muted (or deleted!) all the layers, Halion would still play the same “patch”. And I don’t mean something like a stuck note, I mean that it behaved like the program remain the same and everything I did after duplicating the layer had absolutely no effect (as I said, not even deleting all the layers in the program).
You can see in the screenshot I attached that although the program is completely empty, I can still play the program I had loaded before this bug appeared.