The following are active issues for Halo: Reach as of 7/12/2023 in build 1.3232.0.

User Interface (UI)

When zooming in with the Target Locator, the scope's compass is not visible at the bottom of the screen.
Any camera turning caused by a view angle restriction while in a vehicle passenger seat will stutter above 60 FPS.
Players are unable to enter the gameplay after setting language to Portuguese, Japanese, Chinese, or Korean.
- For Steam, please see troubleshooting steps (Full article).

Gameplay

After leaving then rejoining an Escalation Slayer match, the rejoining player will start with the first weapon regardless of which weapon they had prior to leaving.
- Upon dying or killing another player, the rejoining player will advance to the weapon they had prior to leaving the match.
While flying a Seraph, the camera will zoom in and out when using the alternate fire and boosting at the same time.
The blooming effect around light sources is larger than in the original release of Halo: Reach.
Moving from an enclosed area to face an open area in any map or Campaign mission causes a significant drop in performance. This is most common for PC players with unlimited framerates.
Player models appear to briefly desync when moving after an assassination.
When entering an elevator in co-op or Multiplayer, players will briefly appear to play a falling animation.

New - When a player exits a Campaign Co-Op session comprised of at least three players, the other players' screens may freeze.
- Workaround: close and relaunch Halo: The Master Chief Collection.
Mission progress resets to the beginning of the mission when selecting Resume Campaign after switching between an Xbox One console and an Xbox Series X|S console.
Cutscenes during "Tip of the Spear" can see performance drops using AMD graphics cards.

New - The "Boot Player" prompt may continue to appear after the player initially dismisses it if they were killed by a teammate during a Firefight match with no lives remaining.
New - Rarely, the movement animations for both Brutes and Grunts will break after they exit a drop pod during a Firefight match.