My first guess is that the assembly is using a lightweight representation of the part. Try right clicking on the component node in the assembly navigator and see if the option "show exact" displays in the pop up menu.
Select "Menu > Preferences > Visualization > Faceting (tab)".
Under the Part Settings section, what do you have set for "Shaded Views". I suspect it's set to "Part". If it is, change it to View and see if that cleans up the display.