The portal sometimes produces an error, after that the project seems to be gone, but not the vault. But after a few minutes the vault disappears as well so the error is most probably a timeout in the portal.
Make sure you delete the data first otherwise you get an unspecified internal error.
As admin add yourself to the group, you can't delete (at least via webdav) without explicit membership.
Delete the Movement Sciences and Joris projects.
Will keep a copy for a few months, to make sure.