This applies to the Liquid Mix
MOTU Digital Performer uniquely handles plugins depending upon whether the plugin GUI is open or closed. When a plugin GUI is open, audio passes through the plugin in real-time using the buffer size set in the Audio Preferences.
When the plugin window is closed, it uses a fixed buffer length larger than the maximum 1024 samples allowed by Liquid Mix.
However, there is an option available in each Digital Performer plugin window which allows for plugins to always run in realtime. Enable this option in all your Liquid Mix plugins, as shown in the screenshot below.