Switching to this mode fixed it (shown below):
Changing the "Max" control also fixed it (shown below):
It's worth noting that on the curve type with no breakpoints in the middle, the line doesn't stretch quite as far horizontally. This makes the Y value slightly above 0 when the X value was 0 (which aligns with the issue in the sound), however I find this strange as the visualisation on the device shouldn't actually alter it's function.
Either way, it's a pain to change all of these parameters whenever I want to use any of the Spitfire Audio MPE Instruments (as it's like this with all of them) - I'm asking for either a workaround or for the "bug" to be fixed. Thanks!
