Second flat tie note does not change the first note

r3020

1. Open this file
2. add a B in the second measure
3. Select second note and press arrow down or click on flat in the toolbar
4. If you click on each tied note you'll hear that they don't sound the same (bad for tied notes)
5. Save
6. Reload

Expected result : first two notes tied and Bb (?) and a B in the next measure
Actual result : First and third notes are tied over the second one.