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[David J. Potter]

Like Allen has suggested it has to be some setting, so the best general advice is to really look at the layer, object and other possible settings, find from which vector it is being ordered to look as it does and then take the indicated action.
It might be a bug but it is probably just a setting that you assumed is one way but is otherwise than you supposed.
You find it by looking and confronting what IS there as opposed to assuming.

DJP