There is a body with Translucency set. If turning Transparency OFF in Visualization Preferences, and then select and deselect the body, the transparency will be restored (the transparency will return to ON).
Reproduced Steps:
1. Menu > Edit > Object Display > after select a sold body, OK > General tab > Shaded Display > set Translucency to any value > OK
2. File > Preferences > Visualization > Rendering > Graphics > Translucency=OFF
3. Select the solid body in Graphic window
3. Deselect the selection(ex. re-select the solid body with Shift key)
This behavior is due to a problem that occurred in NX 1926 ~ NX 2306 and lower, and has been fixed in NX 2312.
Workaround : again, set Translucency to OFF( as step 2 above)
Notes**Please refer to PL8794230 for Japanese article.