Cancelled accidentals not shown

Sometimes MuseScore doesn't show cancelled accidentals when the key signature changes. There seem to be two distinct (but perhaps related) issues here.

Steps to reproduce:
1. Create a new score from scratch and add a single instrument, e.g. flute.
2. Choose a key signature of D major (two sharps).
3. Choose a length of 12 bars. MuseScore should show 12 empty bars, all on a single line.
4. At bar eleven, change the key signature to G major (one sharp). The C sharp is cancelled with a natural sign as it should be.
5. Select all, then repeatedly Add More Stretch until bar eleven has overflowed onto the second line.
Notice that the C natural sign cancelling the C sharp has disappeared. It should appear at the end of the first line, to the right of the final bar line, along with the new key signature. The final bar line of this line should be positioned slightly to the left of the end of the staff to accommodate the cancellation naturals and the new key signature. (First issue.)
6. Now Add Less Stretch until bar eleven is back on the first line.
Notice that the C natural has not reappeared. It seems to have been lost permanently. (Second issue.)