So, after some back and forth with Synthogy, I've got them to address the buzzing issue. When I told them that the buzzing was caused through realtime rendering instead of offline, the programer fixed a couple of things and, by the latest update of the engine on Windows, the buzzing is gone! I can both play my American Concert D and the German D without any type of buzzing in the produced audio.
But it seems like my CPU power has gone a bit weaker after the update. Not only am I hearing slight cracks and pops when playing passages with dense notes, but the same can be heard on my Garritan CFX library. It used to be that the CFX was the most smooth library I've ever ran, but it even now starts to have little dropouts and the like. Could it be that there's some "aftershocks" caused by some CPU overload? I don't know.
But this new Ivory III update has somehow made me like the Ivory III experience, if only I had a better CPU / more powerful computer. I guess I'm beginning to see the end of days for this laptop, it's drawing near.
But for now, I can still run American Concert D and Ravenscroft without CPU problems. So better to continue using the device.
So much for now. I'm keeping the German D despite running into problems using it. Now all I need is either for the fans or keyboard to break down, or more software to have dropouts and crackles. Then I'll be on the market for a new powerful machine!