Maximise button in Native Titlebar

I’ve got an audio plug-in with a Standalone version using the native OS titlebar, but there appears to be a bug with using setUsingNativeTitleBar(true) in JUCE on Windows. For some reason the maximise button is always disabled (I’d like to it be enabled), even when I’ve also set
setSize (900, 600);
setResizeLimits(900, 600, INT_MAX, INT_MAX);
setResizable(true, false);

Interestingly on MacOS, the maximise button works just fine, so it only affects the Windows build. How can I fix this?