In 3D Plotting, some flanges are displayed as valves instead of the normal "2 disc" flange notation.

I've double checked that the flanges are entered in correctly. e.g. Model->Valve->FLANGE, FLG, 300
(Diameter and Wt are 2" and s respectively)

Is this a geniune Caesar 4.4 bug or am I missing something??

The "Plots" offered by CAESAR II are not I repeat are not intended to be artists rendering as in a 3d CAD piping package.

A ridgid element with weight is plotted with a volume. If it is long enough it will plot as a valve otherwise a flange.

So don't let this bother you... your ridgid elements have weight and are being plotted correctly.