The undo button on the editor can be mistaken for the typical "undo what I just did" rather than the actual function of reverting the row to the previous state.
It should be clear to the user what it does - revert?
It should consider the instance of a user having edited the field before pressing it (should it be disabled?)
Release test 4.0 6fb744a5b93200ee1f15fb9d651c593f53b08190
Chrome Version 54.0.2840.100 (64-bit)