When locking or fixing traces, the graphics for those traces do not change according to the settings in the Display Control under the Graphic tab > Fixed & Locked patterns. The display change does work correctly on vias.
I don't see this issue myself. I suggest you contact Mentor Customer Support who can look into your specific use case.
I turned the display patterns to outline and issue went away. If you set your display patterns to solid, you should be able to reproduce.
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