I have the same situation with errors on box 18 - 20 on W-2 enty because of two lines for the same locality. The entries are legit for reasons I won't go into here. I found a solution is to open up the form (upper right "Forms" button if using step-b-step). Scroll down to box 20. On one of the identical entries, add a space after the name (this won't work on the Step-by-Step as it appears to remove any trailing spaces). Switch back to Step-by-Step. No more warning message.
I am not a tax expert by any means and I like to have my entries in Turbo Tax to match exactly as the W-2. Maybe someone with more knowledge can comment on this work-around.
