Animation clip in wrong pose

So I have a book in my game with rigged, animated pages. I've got it set up so you can manually turn the pages in-game.

Now, I'm fairly new to Blender, which is what I used for the animations.
I think there's something wrong with my export settings, as one part of the animation timeline has a somewhat different motion after being exported. Basically, when a page is supposed to be still (for about 10 frames), it jiggles a bit instead, even though it's completely still in blender.

So I figure, hey, it's an entirely still part of the animation anyway, I could just turn one frame into its own animation clip and just use that.
But for some reason, the moment I make that animation clip any shorter than 10 frames, the animation doesn't render properly in-game.
The animation clip is triggered in MechAnim (I have the little animator window popped out), but the actual pose is from a completely different part of the timeline.

Does anyone know what's going on and how I can fix this?