Whenever a user changes the title of a referenced node during the edit of that node you will receive a title mismatch error. But this doesn't explain how the user can resolve this error.
It would be more helpfull to explain they can "research the title" OR if they are shure of their selection they can "just use [nid:n] value". This is because the user is unaware that the title may have changed by somebody else and researching the title may be unsuccesfull. So this user should be informed of the option to use the [nid:n] value.
The error message like it is now leads to people not being able to save their node.