The item cannot be removed because it has been modified externally

Reproduce:

I was quickly adding and renaming folders under images. Now I seem to always get "the item cannot be removed because it has been modified externally" bug when adding a folder.

Go to:
cmstest.onehippo.com
go to folder:
> images > hippos2 > a > b > d > e > fsd...
Add another folder

you get the error:
Expert technical details:
javax.jcr.InvalidItemStateException: 32329e5a-45f8-4933-8e59-5c3fa163cde8: the item cannot be removed because it has been modified externally