An error occurred while attaching module (Dynamicweb.Frontend.Content)

System.ArgumentException: An item with the same key has already been added.
   at System.ThrowHelper.ThrowArgumentException(ExceptionResource resource)
   at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
   at Smartpage.Ecommerce.Repo.UnitService.InitializeUnits() in C:\Repos\Kruuse\Smartpage.Ecommerce\Repo\UnitService.cs:line 59
   at System.Lazy`1.CreateValue()
   at System.Lazy`1.LazyInitValue()
   at Smartpage.Ecommerce.Repo.UnitService.get_UnitIndex() in C:\Repos\Kruuse\Smartpage.Ecommerce\Repo\UnitService.cs:line 16
   at Smartpage.Ecommerce.Repo.UnitService.GetStockAmountForVariant(String productId, String variantId) in C:\Repos\Kruuse\Smartpage.Ecommerce\Repo\UnitService.cs:line 34
   at Smartpage.Ecommerce.Providers.VariantStockLevelProvider.FindStockLevel(Product product, String unitId, StockLocation stockLocation) in C:\Repos\Kruuse\Smartpage.Ecommerce\Providers\VariantStockLevelProvider.cs:line 32
   at Dynamicweb.Ecommerce.Stocks.StockLevelManager.FindStockLevel(Product product, String unitId, StockLocation stockLocation)
   at Dynamicweb.Ecommerce.Products.Product.GetUnitStock(StockLocation stockLocation, String unitId)
   at Dynamicweb.Ecommerce.Frontend.Renderer.RenderProduct(Product product, Boolean extendedProperties, Template template, Int32 loopCounter, Boolean renderRelated, String productUrl, Int32 quantity, Int32 wishListId, Boolean renderPublicList, Boolean isRecursiveCall, Lazy`1 categoryFieldSorting, Int32 orderLineOfProductCount, RenderingContext renderingContext, String unitId)
   at Dynamicweb.Ecommerce.Frontend.Renderer.RenderProduct(Product product, Boolean extendedProperties, String unitId)
   at Dynamicweb.Ecommerce.Frontend.Frontend.EcomRender()
   at Dynamicweb.Ecommerce.Frontend.Frontend.GetContent()
   at Dynamicweb.Frontend.Content.GetModuleOutput(Paragraph paragraph, PageView pageview)