Merchant Navy not working

[swimslave]

I am playing on an Island map as the Hawaiins and have activated Merchant Navy. However, while the yield icons are telling me that all my city tiles are now producing 5 hammers, I am still only receiving two in my production yield.

Has anyone else noticed this?

I just loaded the game from a previous save if that matters.

 

[The_J]

Please take a look at the city center tile. The additional hammer should show up there.