BUG: Compare sees a suprious duplicate object definition

I am attempting a compare between a source scripts folder and a database; the folders contain a Visual Studio Db project (athough the compare dialog detects it as a RedGate compare folder rather than a VS DB project). The comparison fails with the message 'A duplicate definition was found for the user defined type [dbo].[Foo]. Ensure that case sensitivity....'
There is no duplicate definition of the UDT, although there is a table called Foo in a different schema. If I reverse engineer scripts from the database and then use those to do a compare then no duplicate is detected.