I also had some place names that wouldn't merge, but I finally figured out a way that they would. Hopefully this will work for you too. Taking all of the duplicates of a place one by one (as a set),
1. Delete the Location field's data.
2. In the Name field, rename the place to RenameMe (or any other easy to find name).
Once you have that set of duplicates all renamed, there should only be one Place named RenameMe. If not, go ahead and merge them so there's only one place named RenameMe. Then change RenameMe in the Name field to the original place name.
1. Delete the Location field's data.
2. In the Name field, rename the place to RenameMe (or any other easy to find name).
Once you have that set of duplicates all renamed, there should only be one Place named RenameMe. If not, go ahead and merge them so there's only one place named RenameMe. Then change RenameMe in the Name field to the original place name.