Included Music 5000 disc image is broken

[rhalkyard]

The Music 5000 disc image included with BeebEm (UserData/DiscIms/M5000-4.ssd) appears to be broken - you can play existing songs just fine, but the Staff Editor clears the staff every time you move from the command prompt to the staff, making it impossible to edit or create scores.

According to https://stardot.org.uk/forums/viewtopic.php?p=217350#p217350, this is a problem introduced by a patch intended to defeat AMPLE's copy protection. The linked post includes a new disc image, distributed with B-Em, with an alternative copy-protection patch that does not exhibit this issue.

Steps to reproduce (using an emulated system with Sideways RAM and an *SRLOAD command in ROM):

1. Load DiscIms/M5000-4.ssd
2. Boot disc TWICE with Shift-Break (first boot loads AMPLE into SWRAM, second boot starts AMPLE and loads modules from disc)
3. Select the "Staff Editor" item from the main menu
4. Press Tab to move the cursor to the staff
5. Enter something on the staff (e.g. type c then q to enter a clef and a 4/4 time signature)
6. Press Tab to move the cursor to the % prompt
7. Press Tab again to move the cursor to the staff

Expected behavior Staff contents are preserved, allowing further editing.

Actual behavior Staff contents are cleared, as if the CLEAR command was entered at the prompt.