is it me, or are the white splotches only on the glass areas?
if so, have you tried changing the glass to something else (possibly non transparent) and are there still these blobs? if not then shows it's down to the glass material - try varying the shinyness and/or opacity...
Also... how are the glass panels located in the assembly? There has always been rendering errors with glass if it is touching (or intersecting) another object - make sure the glass is inside the border and not mated with a zero offset with anything (something tiny like 0.01mm will do).
So it's not just snowing in the trolley