Aniblock won't move!

Deadly Buda

All of a sudden, I can't move the topmost aniblock for a few of my characters in a scene I'm working on. Subtracks work fine. But, as soon as I try to move the top aniblock, it's locked by a red line on the right hand side. If I delete it and add another, the aniblock on that track snaps to zero as well. They won't slide, and I don't have the "lock" icon selected. 

Is this a bug or some feature I haven't encountered in the last year?

Deadly Buda

Hmm... I changed layout from packed to sparse and now they move. Not sure why this is.