Variaudio Segment Time Stretch sometimes locked

I must be missing something.
Sometimes when I open a mono audio track segment into the VariAudio editor, I can’t time stretch individual notes - they’re “locked” from stretching by what looks like hitpoint markers above…but they’re not hitpoints? Are they just note boundaries? I deleted generated hitpoints but these remain. So are these little black markers the cause of the “locking” or just a visual symptom? See screenshots below. The weird thing for me is that this stretch-prevention isn’t always happening. I can’t predict what I’m doing to “lock” the track notes. Can anyone please illuminate for me what I’m missing? Searches haven’t turned up anything yet… [Cubase Pro v12.0.5].

Thank you!
Screen Shot 2023-01-06 at 3.32.45 PM