v0.6.9.2-8993f96-sw
InvalidOperationException: Material Fertilizer is already loaded.
Timberborn.TimbermeshMaterials.MaterialRepository.LoadMaterials (System.Collections.Generic.IEnumerable`1[T] specifications) (at <bb71dec75aba4c10a33a51c1f8aa0daf>:0)
(wrapper dynamic-method) MonoMod.Utils.DynamicMethodDefinition.Timberborn.TimbermeshMaterials.MaterialRepository.Load_Patch2(Timberborn.TimbermeshMaterials.MaterialRepository)
MorePaths.Core.PrefabGroupServicePatch.EarlyLoad[T,TT] () (at <70ac98dfe4484f3d8d0e1f484fe0affb>:0)
MorePaths.Core.PrefabGroupServicePatch.Prefix () (at <70ac98dfe4484f3d8d0e1f484fe0affb>:0)
(wrapper dynamic-method) MonoMod.Utils.DynamicMethodDefinition.Timberborn.PrefabGroupSystem.PrefabGroupService.Load_Patch2(Timberborn.PrefabGroupSystem.PrefabGroupService)
TimberApi.SpecificationSystem.EarlyPrefabCollectionPatches.GameEarlyLoadPrefabCollection.Load () (at <29bd38ea98344a93be50513bcce5b431>:0)
TimberApi.SingletonSystem.SingletonLifecycleServicePatcher+<>c.<LoadAllPrefix>b__0_0 (TimberApi.SingletonSystem.ITimberApiLoadableSingleton singleton) (at <da74fda7d92d465e907bb48b367b09f8>:0)
TimberApi.SingletonSystem.SingletonLifecycleServicePatcher.LoadSingleton[T] (System.Collections.Generic.IEnumerable`1[T] singletons, System.Action`1[T] action) (at <da74fda7d92d465e907bb48b367b09f8>:0)
TimberApi.SingletonSystem.SingletonLifecycleServicePatcher.LoadAllPrefix (Timberborn.SingletonSystem.ISingletonRepository ____singletonRepository) (at <da74fda7d92d465e907bb48b367b09f8>:0)
(wrapper dynamic-method) MonoMod.Utils.DynamicMethodDefinition.Timberborn.SingletonSystem.SingletonLifecycleService.LoadAll_Patch1(Timberborn.SingletonSystem.SingletonLifecycleService)
Timberborn.SingletonSystem.SingletonLifecycleAdapter.Start () (at <83c35e71bcfd4e238b263c72f0ec19cd>:0)

v0.6.9.2-8993f96-sw
InvalidOperationException: Material Fertilizer is already loaded.
Timberborn.TimbermeshMaterials.MaterialRepository.LoadMaterials (System.Collections.Generic.IEnumerable`1[T] specifications) (at <bb71dec75aba4c10a33a51c1f8aa0daf>:0)
(wrapper dynamic-method) MonoMod.Utils.DynamicMethodDefinition.Timberborn.TimbermeshMaterials.MaterialRepository.Load_Patch1(Timberborn.TimbermeshMaterials.MaterialRepository)
(wrapper dynamic-method) MonoMod.Utils.DynamicMethodDefinition.Timberborn.SingletonSystem.SingletonLifecycleService.LoadSingletons_Patch2(Timberborn.SingletonSystem.SingletonLifecycleService)
(wrapper dynamic-method) MonoMod.Utils.DynamicMethodDefinition.Timberborn.SingletonSystem.SingletonLifecycleService.LoadAll_Patch1(Timberborn.SingletonSystem.SingletonLifecycleService)
Timberborn.SingletonSystem.SingletonLifecycleAdapter.Start () (at <83c35e71bcfd4e238b263c72f0ec19cd>:0)

Seems to be the same.

Thank you both for reporting this. Unluckily I cannot reproduce it.
I suggest you either:
- Verify the integrity of the game files (right click on the game -> properties -> installed files -> verify integrity)
- unsuscribe - subscribe again
- manually delete the mod folder and download it again.

Also ensure you don't have multiple copies of the mod (though this would normally result in a different error).

Finally, if the issue persists, please provide the faction you are using, any specifics (did you reload a game, or start a new one, etc.)

The final idea I have is that another mod is (re-)loading the material as well, but I don't know of such a mod.

Hello! I released 0.3.2 now that resolves a conflict with the mod: "Append Vanilla Resources" that caused the material to be loaded twice. I hope this resolves your cases.
Let me know if anything else comes up.