Undo of concert pitch produces incorrect transposition

Ubuntu 14.04, GIT commit: 0a59df0

1) new score for a Bb instrument, C major concert (transposed key is D)
2) enter a D in first measure
3) Concert Pitch - the D transposed to C and so does the key, as expected
4) Undo

Result: the key reverts to D, but the note stays C (displayed with an explicit accidental). Status line reports pitch as D.

This is not unique to the key of C, so it's not just the weirdness with how we handle C major key signatures causing this. Lots of other variations on this bug can be seen with other sequences of events. But the basic idea is that Undo of the Concert Pitch doesn't do its job correctly.

Borderline critical as it can leave score in an inconsistent state, potential for data loss. However, it does seem that it is a display-only anomaly. Things correct themselves on save/reload or if you press Concert Pitch again. Each note corrects itself if you, for example, use the arrow keys to change a pitch.

From what I can tell, the TPC1 and TPC2 are both correct. For some reason the line & accidental just aren't being updated.