As @ChrisMorgan suggests, it could be a number of things.....such as section cut not being perpendicular to the feature, or the feature not being a continuous radius, or even the feature not being concentric.
Very difficult to offer a reasonable diagnosis, without the PAR & DFT files to verify against.
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How was the dish modeled? It would appear that for some reason it is not a portion of a sphere, which it looks like it should be. If it is indeed a sphere, the only way the radius could differ is if the section is NOT PERPENDICULAR to the view and I think that is impossible by definition for a section view.
Its just a curved cutout Dan, i initially thought it was as sphere which might make it more likely to be an error. Either the circle profile has come in from create 3d or similar and is not quite round after a file conversion. or it is on a plane not quite perpendicular to the model. The cutting plane as suggested would only make a difference it was actually a sphere.
Hard work without the model / dft.