Channel group expander error

[Sctiger]

I was updating one of my old sequences to include the new pixels.  Everything has been going fine until this point. I was reaching the end of one particular sequence and for the big finale I copied/pasted a particular color that I wanted to use with a definitive start and stop.  When the sequence played back, the pixels continued to flash even when the channel isn't showing anything in the grid.  When I tried to expand the channels out, I get a pop up that says "Channel group expander error" with the text "unknown expander node map key".  Any thoughts?  Just when I thought I was getting it! lol