I'm used to the duplicate error message- and understand the usual cause.

For the current producion I 'added' 3 projects to the production - those projects may well have had the same UID - not sure how they were created - but it should have given a unique UID when adding to project I think? As it is it is seeing them as 3 duplicates.

Not a problem to sort but annoying. Should be a warning when adding to project.