Do you have the project saved?
Did you check to see if there's just spaces at the end of the names?
i don't think so, in fact, the costume duplicated itself everytime that i added a shape to it
i didn't save the project yet when it happened
No, I want you to save it after it happens! :~)
yes but i also deleted the costume's copies
Oh. Well, if you can reproduce the problem, then save the project!
Saving wouldn't do anything, it's a graphical glitch. This has happened to me multiple times, but that was by editing a costume not currently selected.