Not Enough Items (NEI) Crash: IllegalAccessError on PotionHelper$MixPredicate

What the log looks like

java\.lang\.IllegalAccessError: tried to access class net\.minecraft\.potion\.PotionHelper\$MixPredicate from class codechicken\.nei\.util\.helper\.potion\.Potio
at codechicken\.nei\.util\.helper\.potion\.PotionRecipeHelper\.init\(

How to fix it

1. Update Not Enough Items (NEI) and CodeChickenLib to their latest 1.12.2 versions from CurseForge or Modrinth, and delete the old jar files from your mods folder.
2. Update Minecraft Forge 1.12.2 to a newer recommended build (such as 14.23.5.2859 or 14.23.5.2860) to fix the Forge bug that prevented Access Transformers from applying.
3. Update Just Enough Items (JEI) to its latest 1.12.2 release, since NEI in 1.12.2 runs as an add-on on top of JEI.
4. If you do not specifically need NEI's extra overlays or utilities, remove NotEnoughItems from your mods folder and use JEI on its own.

Check your own log