The shadow catcher bug should be resolved with the next build, which we're trying to get out soon. I'll look into the fog issue, thanks for the report. The glass simple preset uses newton's rings, which isn't supported in Viewer, so it may look different. You should try the refraction shader for glass though, it's way…
The shadow catcher issue should be resolved 3.04 B2, but there may be some specific instances where it still isn't working. Can you please email support@marmoset.co with an example scene that shows the shadow catcher problem and a detailed explanation of what is happening? The best way to do this is to go to File -> Export…