Apex Animation Works Fine, Till You Look Away

I have a curtain that is using an Apex animation as a cloth to open and close. Works well, until I look away from the curtain, then look back at the curtain. The curtain kind of jumps and becomes completely gibbered. Is there a way I can keep this from happening? Perhaps freeze the curtain when the animation stop and unfreezes when an animation starts again? Or is it some type of setting that is making it jump when the camera is not in view? Or is this a bug?

Here is a view after it opens correctly.

Here is a view when you look away, then look back at the curtain.