Sigh. Left hinge cracked all the way through. Was FLAWLESS, not even a stress crack, last time. And the right one's got a slight stress mark now.
Theory: it's time, not transformations. I've only transformed mine like 6 times---once a month to change poses. It's sat for a few weeks since the last transformation. And trust me, nobody here is slower, more paranoid, or more careful than me when transforming a V2 VF-1.