Why are the plug-in knobs snapping all the way up or down?

That's a bug. As far as we know, it only affected version 5.3.1 on Windows and it didn't happen for everyone.

This should be fixed in as of version 5.3.2, so you can simply install the latest version to fix it. You can find the latest downloads on your Soundtoys account (if you've set it up with an iLok account), in your order confirmation email, or on our full download page here.