What am I doing wrong?

[Ceciliabr]

@Hansmex

As far as I can see from your example renders, the problem lies only with the reflections from the plate. The glasses appear to be the same in all four pics (unless my poor eyesight plays tricks on me).
This being the case, I think an area render function would be a good solution. I use area render a lot with other programs, when only small parts of a picture requires maximum render quality.

cec