After upgrading to fabric-api-0.86.0+1.20.1.jar, the GUI & hand items break, displaying purple/black checkerboard box.

I could reproduce the issue:
[21:30:01] [Worker-Main-11/WARN]: Unable to load model: 'minecraft:item/axolotl_bucket_wild' referenced from: minecraft:item/axolotl_bucket_wild: java.lang.NullPointerException: Cannot invoke "net.fabricmc.fabric.impl.client.model.loading.ModelLoadingEventDispatcher.loadModel(net.minecraft.class_2960)" because "this.fabric_eventDispatcher" is null [21:30:01] [Worker-Main-11/WARN]: Unable to load model: 'minecraft:item/axolotl_bucket_gold' referenced from: minecraft:item/axolotl_bucket_gold: java.lang.NullPointerException: Cannot invoke "net.fabricmc.fabric.impl.client.model.loading.ModelLoadingEventDispatcher.loadModel(net.minecraft.class_2960)" because "this.fabric_eventDispatcher" is null [21:30:01] [Worker-Main-11/WARN]: Unable to load model: 'minecraft:item/axolotl_bucket_cyan' referenced from: minecraft:item/axolotl_bucket_cyan: java.lang.NullPointerException: Cannot invoke "net.fabricmc.fabric.impl.client.model.loading.ModelLoadingEventDispatcher.loadModel(net.minecraft.class_2960)" because "this.fabric_eventDispatcher" is null [21:30:01] [Worker-Main-11/WARN]: Unable to load model: 'minecraft:item/axolotl_bucket_blue' referenced from: minecraft:item/axolotl_bucket_blue: java.lang.NullPointerException: Cannot invoke "net.fabricmc.fabric.impl.client.model.loading.ModelLoadingEventDispatcher.loadModel(net.minecraft.class_2960)" because "this.fabric_eventDispatcher" is null [21:30:01] [Worker-Main-11/WARN]: Unable to load model: 'mavm:item/axolotl_bucket_lucia' referenced from: mavm:item/axolotl_bucket_lucia: java.lang.NullPointerException: Cannot invoke "net.fabricmc.fabric.impl.client.model.loading.ModelLoadingEventDispatcher.loadModel(net.minecraft.class_2960)" because "this.fabric_eventDispatcher" is null [21:30:01] [Worker-Main-11/WARN]: Unable to load model: 'mavm:item/axolotl_bucket_wilder' referenced from: mavm:item/axolotl_bucket_wilder: java.lang.NullPointerException: Cannot invoke "net.fabricmc.fabric.impl.client.model.loading.ModelLoadingEventDispatcher.loadModel(net.minecraft.class_2960)" because "this.fabric_eventDispatcher" is null [21:30:01] [Worker-Main-11/WARN]: Unable to load model: 'mavm:item/axolotl_bucket_golden' referenced from: mavm:item/axolotl_bucket_golden: java.lang.NullPointerException: Cannot invoke "net.fabricmc.fabric.impl.client.model.loading.ModelLoadingEventDispatcher.loadModel(net.minecraft.class_2960)" because "this.fabric_eventDispatcher" is null [21:30:01] [Worker-Main-11/WARN]: Unable to load model: 'mavm:item/axolotl_bucket_green' referenced from: mavm:item/axolotl_bucket_green: java.lang.NullPointerException: Cannot invoke "net.fabricmc.fabric.impl.client.model.loading.ModelLoadingEventDispatcher.loadModel(net.minecraft.class_2960)" because "this.fabric_eventDispatcher" is null [21:30:01] [Worker-Main-11/WARN]: Unable to load model: 'mavm:item/axolotl_bucket_skulk' referenced from: mavm:item/axolotl_bucket_skulk: java.lang.NullPointerException: Cannot invoke "net.fabricmc.fabric.impl.client.model.loading.ModelLoadingEventDispatcher.loadModel(net.minecraft.class_2960)" because "this.fabric_eventDispatcher" is null [21:30:01] [Worker-Main-11/WARN]: Unable to load model: 'mavm:item/axolotl_bucket_red' referenced from: mavm:item/axolotl_bucket_red: java.lang.NullPointerException: Cannot invoke "net.fabricmc.fabric.impl.client.model.loading.ModelLoadingEventDispatcher.loadModel(net.minecraft.class_2960)" because "this.fabric_eventDispatcher" is null [21:30:01] [Worker-Main-11/WARN]: Unable to load model: 'mavm:item/axolotl_bucket_glowxolotl' referenced from: mavm:item/axolotl_bucket_glowxolotl: java.lang.NullPointerException: Cannot invoke "net.fabricmc.fabric.impl.client.model.loading.ModelLoadingEventDispatcher.loadModel(net.minecraft.class_2960)" because "this.fabric_eventDispatcher" is null [21:30:01] [Worker-Main-11/WARN]: Unable to load model: 'mavm:item/axolotl_bucket_white' referenced from: mavm:item/axolotl_bucket_white: java.lang.NullPointerException: Cannot invoke "net.fabricmc.fabric.impl.client.model.loading.ModelLoadingEventDispatcher.loadModel(net.minecraft.class_2960)" because "this.fabric_eventDispatcher" is null [21:30:01] [Worker-Main-11/WARN]: Unable to load model: 'mavm:item/axolotl_bucket_cyanide' referenced from: mavm:item/axolotl_bucket_cyanide: java.lang.NullPointerException: Cannot invoke "net.fabricmc.fabric.impl.client.model.loading.ModelLoadingEventDispatcher.loadModel(net.minecraft.class_2960)" because "this.fabric_eventDispatcher" is null

Appreciate the mod! Thanks for taking a look!

Fixed! thanks to @LunaWasFlaggedAgain for the pull request with the fix. Will be published soon.

Thanks folks! Appreciate the hard work! :)

Greetings, AkashiiKun! How goes the fix? Anything I can do to assist? I'm not a developer, but if we're just talking about incrementing/decrementing /changing links, etc. I may be able to lend a hand there.

Right now i'm on vacation, i'm sorry. We'll try to figure out a fix as soon as possible.

Ah! Apologies, my friend! Have a great restful vacation. :)

The fix crashes with forge unfortunately, #8