Iris Shaders Crash: IllegalStateException: Already in a group

What the log looks like

java\.lang\.IllegalStateException: Already in a group
batchedentityrendering\.impl\.ordering\.GraphTranslucencyRenderOrderManager\.startGroup

How to fix it

1. If you have Not Enough Crashes installed (look for `fudge.notenoughcrashes` in the crash report), remove it from your `mods` folder and trigger the crash again so Minecraft generates a clean report showing the real underlying error.
2. Temporarily turn off shaders (press `K` in-game or edit `config/iris.properties` and set `enableShaders=false`) to confirm whether the conflict only happens during active shader passes.
3. Update Iris, Sodium, and any custom player/entity rendering mods (such as Customizable Player Models, GeckoLib, or armor mods like Ad Astra) to the latest versions for your Minecraft release.
4. If the crash happens when equipping a specific modded item or using Customizable Player Models, disable CPM's custom hand/shader compatibility settings or remove the conflicting visual mod while using shaders.
5. Check `logs/latest.log` right above the `Already in a group` stack trace for an earlier `ERROR` or `Exception` thrown during entity rendering, which points to the specific mod or entity that failed mid-render.

Check your own log