Litmus has been used by my team for a while. For a long time, every time we saw a visual mistake in Litmus, we would pull out our hair trying to fix it. We didn't do it most of the time. We tried it in all the browsers and clients we had access to, but we could never get the error in Litmus to happen again. Is this something that happens often? If so, how have all of your visual client previews gone with these services?