The Halo: CEA portion of the Master Chief Collection is quite buggy atm according to
Windows Central. Excerpt below:
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Halo: Combat Evolved Anniversary PC audio issues
Some of the worst bugs in the game are the audio ones, which currently affect a large portion of both Campaign and Multiplayer content. Music is reported to loop or cut off incorrectly, and will sometimes even not play at all. In addition, sound effects will sometimes play at incorrect volumes, and may also glitch out or play the wrong sound effect entirely (for example, quickly firing the Plasma Pistol will cause the overcharge sound even though you never overcharged the weapon). These issues can temporarily be resolved by reloading your level checkpoints or restarting the game, but they will eventually return. In addition, it has also been reported that audio effects don't properly echo or reverb when they're supposed to, which is a problem that players can't solve in any way, temporarily or otherwise.
According to 343 Industries' support site for the Master Chief Collection, the problems with the audio are being worked on and will be addressed in a future update.
Halo: Combat Evolved Anniversary PC gameplay issues
There are a variety of different known gameplay bugs being experienced by players of Halo: Combat Evolved Anniversary on PC. The most severe of these is a rather bizarre issue with weapons that lose accuracy the longer they're continuously fired, such as the Magnum, the Assault Rifle, and the Plasma Rifle. The higher your framerate is, the faster these types of weapons will become inaccurate to shoot. This issue affects Campaign and Multiplayer both, and thus, causes the gameplay experience of both modes to be severely incorrect.
Another known issue is that weapons can become partially or full stuck inside of walls, usually due to being launched into them by explosives. Players can solve this by restarting a checkpoint to before the time the weapon got stuck, though if they load a checkpoint after it happens (or are playing Multiplayer) they will be out of luck.
A problem unique to the Campaign is that some scripted events in levels, such as important doors opening, can take longer to trigger than they are supposed to.
Finally, some players are reporting that they can't access Halo: Combat Evolved Anniversary's Terminals after respawning, restarting a checkpoint, or playing missions one after the other. Players can solve this issue temporarily by restarting the game.
343 Industries is aware of all of these gameplay issues and is currently working on a permanent fix.
Halo: Combat Evolved Anniversary PC technical issues
Players are reporting some technical problems with Halo: Combat Evolved Anniversary on PC. The worst of these are problems with the game freezing, stuttering, and crashing. Players can attempt to make the game run better by lowering graphics settings and using 30 or 60 frames-per-second (FPS) capped instead of unlimited FPS; if issues still persist, users on Steam can try to verify their game files to see if they find a corrupted file in the game folder. If this does not work, or if you are a Windows 10/Xbox Game Pass for PC user, the final step is to uninstall and reinstall the game. If issues persist beyond this point, players will need to wait for an official fix.
Some folks are reporting that they are having issues installing the game if they participated in the recent Halo: Combat Evolved Anniversary test flight. Players can resolve this issue by uninstalling the old test build.
Players may also experience input lag with controllers, mice, and keyboards. Much has been done recently to try and solve input lag by 343 Industries, but if you're still experiencing problems, you can try turning off uncapped FPS or disabling any additional software you may have running, such as ReShade.
People who try to sync up their Halo: Combat Evolved Anniversary game data between different platforms and services (Xbox, Steam, Windows 10 Store, etc.) may experience loss of Campaign sava data. Currently, there is no known workaround for this.
As with the other bugs, 343 Industries is working to resolve Halo: Combat Evolved Anniversary's technical problems.