COMSOL: Problem in Boundary definition for 2 fluids
 

I have been trying to create a micromixer in COMSOL and I am using water and ethanol, but I am unable to define the same common boundaries for ethanol that I had done for water. An error pops up saying it is overridden, and the boundaries are deselected. Please help me out on this.

Additional info, this 3D CAD diagram of the micromixer has been created in Solidworks and imported via Livelink interface.

Here is a link for the image with the error showing in.
https://www.reddit.com/r/COMSOL/comm..._for_2_fluids/