Here we have a simple plane with a shape key that moves it up and down. The shape key is driven by a bone, so that moving the bone moves the plane along with it. Inexplicably though, when the driver gets close to its mid-point, it jumps off the F-Curve and snaps to 0:
Deleting the driver’s middle keyframe fixes this, but I need that keyframe to be there (it’s actually a stripped-down eyelid rig, which uses a Bezier curve instead of a Linear one).
The bone’s range of motion is quite small, so unless there’s a secret quantum physics feature that comes into play at smaller scales, I’m at a loss as to why this is happening. Here’s the file if anyone’s keen to poke around.
Driver Glitch 1a.blend (2.6 MB)
Thanks for any help!