Glyph addition very slow

Whenever you add a glyph, duplicate, or rename one, it takes about a second, or sometimes forever to finish. I duplicated all A to z, which took some minutes. I think this was once solved but it’s been very slow again. Could you have a look?

I fixed the duplication but the renaming is very fast for me. Can you send me a font and a screencast?

Will be done. Thanks.