So the YM and ES load and display OK in Sierra, but you get a message about an incorrect symbol after the others have loaded? Correct?
I've got a chartbook for the DAX that gives me that message when I load it. I've no idea why, all the charts in the book load OK. Something is telling IB there's another symbol there, and it's a false one. However, it doesn't seem to matter.
It may be something to do with the fact that I'm also loading a daily chart from the Dial Data db in that chartbook, possibly the code is getting passed to IB, which rejects it before it gets passed on to trackdata to be filled?