Hello I think the External Insert plugin is due for a much needed update to fix its behavior. As of now, and since it was released, it is forcing stereo outputs, and if you choose a mono output, it hijacks the second mono output of whatever pair you selected first. Even if you set interleave to mono, External Insert will remain in stereo. To test it, do the following: -Create an audio track, instantiate an External Insert plugin. -Set SEND of External Plugin to a mono output, lets