If we have a metadata with a right limitation (restrict-to) on it, the context is not read, by default, the right is check on "/contributor" context.
Line 1026-1027 of DefaultContentType.java, there is a FIXME comment:
// FIXME use a component for converting the content into a context [...] _rightsManager.hasRight(login, rightId, "/contributor")
Then a user with rights only on orgunits (for ODF plugin) can open the content in edition, but never edit it because fields are all in read-only mode.