See https://github.com/WeAreROLI/JUCE/issues/401

JUCE has some questionable checks regarding the currently focussed window and claims that the plugin window is not focussed if the window belongs to a different process. This used to work in OpenMPT 1.28 and older because we had a "window inside window" architecture. 1.29 no longer needs this architecture, but the new approach breaks those JUCE plugins. For example the context menu popups in Dexed no longer work, same with the dropdown menus in Korg Triton.

We should try creating the whole window on the bridge side (and, if possible, add the menu and stuff back from the OpenMPT side to avoid code duplication), which could potentially also fix bridged plugin UIs in Wine at the same time.