Unfortunately, when you right-click a taskbar item DisplayFusion has to show it in order to show the context menu. It isn't perfect, but it was the only way to make it work with all applications. When middle-clicking the taskbar item, DisplayFusion just tells Windows to launch the application using the same settings as the original application. This leaves the positioning up to the original application, which would explain why it doesn't appear on the second monitor. DisplayFusion currently doesn't have the ability to move an application immediately when it is started via middle-click.

No problem, hopefully in the future I can find a way to work around these issues.