Here is where Andy tells how to correct the target information:

This scenario occurs with enough frequency to justify the Restore Invalid Column References Editor, shown above. The ContactID column with Lineage ID 32 is shown as invalid, but the References Editor located (and suggests) a column with the same name and data type: the ContactID column with Lineage ID 333. In fact, it’s located new columns for all the invalid references (although the error did not report these additional columns).

Click OK to replace the invalid references with the suggested columns

You have several options in the Restore Invalid Column References Editor. One of them is to let the editor try to restore the invalid links but I usually highlight all of the rows listed and click on the delete invalid rows option and hit "Apply" (there is no OK button). This will close the editor and remove the invalid references. When you reopen the target again everything should fix itself and you are on your way.