Montage preview does not stop the previous montage from another slot group

In the Animation Editor, when you open a montage that uses a different slot group, the previous montage keeps playing in the preview, and its notifies keep firing. If both montages have a section with the same name, loop settings for the new montage are also applied to the old one. UAnimPreviewInstance::RestartMontage calls Montage_Play, which only stops montages in the same slot group.

1. Open the attached project.
2. Open AM_TestGroup2_DefaultAndSecond (slot group TestGroup2) and let it play.
3. In the Asset Browser, open AM_TestGroup1_Default (slot group TestGroup1).
4. Watch the viewport.

Expected Behavior: Only AM_TestGroup1_Default plays.

Actual Behavior: AM_TestGroup2_DefaultAndSecond also keeps playing, and its Default section loops and spawns many particles.