RenderTexture being weird

Hello!

I'm having an issue trying to use a render texture with a UI element.

I want to point a camera at a simulated 2D water object. It works just fine in the Scene view, but in the Game view it seems like it clips and freezes the last known pixels in the area that no longer has the water in view.
Think of it as a potion depleting liquid. but the last known pixels stay there..

Here's a screenshot


Notice how the image on the right doesn't contain the transparent area as the liquid goes down..
It's like some kind of culling issue

Any ideas?

Thanks!
-Rocky