Undo of insert first measure corrupts clefs
Ubuntu 14.04, GIT commit: 0dfcac4
The problem might be more general than this, and I can reproduce a number of various symtoms, but here are steps to what I assume is the core issue:
1) new score, treble clef template
2) drag bass clef to first measure
3) select first measure
4) insert measure
6) drag treble clef back to first measure
Result: subsequent systems still show bass clef
7) first measure, note entry
8) enters C C C C C
Result: the C's in the first measure enter correctly, the C in the second measure displays way above the staff as if in bass clef.
As with most clef map corruptions, this is actually not a permanent condition - save/reload fixes it. But who would be brave enough to save a score in this state?