How do you fix Mercer Frey glitch on Xbox 360 Skyrim?

To fix the Mercer Frey glitch in Skyrim on Xbox 360, where he may not appear during the quest "The Pursuit," you can try reloading an earlier save before the quest starts. If that doesn’t work, waiting in-game for a few days or fast traveling to different locations may trigger his appearance. As a last resort, you can also try clearing the cache of your Xbox 360 or reinstalling the game, though these options may risk losing other game progress.