Using SB 8.1.4227.0

When adding files to a project, I used to get a warning message asking if I wanted to add duplicate files. I always said no.

When doing a project today, I missed a DLL in my original build. I highlighted all the DLLs in my source folder to ensure I didn't miss another and clicked add. It asked the question as usual, I answered NO and the files were duplicated.

Closed and started over, the second and every other attempt the message was not asked and the files were duplicated.

Even when I closed SB down and restarted, the message was not asked and dupes were added.

Am I missing something in a setting or ???

Thanks,
Bob Taylor