Compare & Merge can't merge into current

I have one diagram that, when I Compare and Merge to the live database, does not show me the option to "Merge into Current."  I only have options to "Ignore" or "Merge into Target" (the live database).  I'm trying to update the model with recent changes to the database, and I'm unable to do so.

This is the ONLY diagram (of seven) where I'm having this trouble.