Notes tied together via regroup command play back as slurs
To reproduce from scratch:
1. Enter an eighth note, followed by a few quarter notes. The one that crosses the middle of the beat is automatically made into two tied eighths.
2. Select the first of those tied eighths and make it a quarter note.
3. Select the measure and choose Format > Reset Note and Rest Groupings (likely soon to be found under the Tools menu).
4. Play from the beginning.