Corruption in local time signature

From https://musescore.org/en/node/297225

"When trying to create a score with a local time signature of 6/8 (after the main part in 4/4 timing), if I try to fill each measure with two dotted quarter notes I get a series of small erroneous rests at the end of the measure."

To reproduce this issue:
1. Create a new score in 4/4, or use the default "Untitled" score.
2. Apply a local time signature of 6/8 (hold down Ctrl while dragging or double-clicking).
3. Try to fill a measure with two dotted quarter notes.
Result:

This kind of issue has come up before. See #276363: Corruption on duration change of note in measure with local time signature, for instance.