pixel perfect camera error

I'd like use a render texture in my ui filming something else, with the main camera using pixel perfect camera filming that render texture and other ui things.

When I do this, when the other camera moves, the sprites it renders to the render texture jiggle around a lot even with pixel snapping on.

I tried putting another pixel perfect camera on the render texture camera, this made Unity Editor a bit angry and black boxes appeared all over the UI.

Whats the best way to move the other rendering camera so that sprites stay stable?