If that's not working then there isn't too much we can do about it, as it's an issue of interference between the synced drawing onto both monitors (internal and external). There is a preference in the upcoming MixEmergency version 1.5 that will allow you to disable the sync on MixEmergency's full-screen output window which should fix the issue. However, disabling the output sync may result in tearing of the output image. I can't say exactly when 1.5 will be out, but all going well it should be soon-ish.
