Yes, and only when I load the mux saved with Scaler. When I place scaler to new Mux and quit without saving there is no error.
It seems that it also depends of the project template I use - composer template works fine (even customized) - the error appears on custom Synth templates. The Scaler plugin itself works fine though, so I don't worry about that error message.
P.S. Scaler 2.7 is a fresh update so it may contain some bugs we don't know about yet.
I attached the Mux (it needs Scaler 2.7 and BlueArp vst).