We are encountering some instances of the below error, looks like some missing null checks on your behalf in the AddHandlerToCache method
Origin: LogEventBeforeSave - Action: Parsing - Category: Application - ExceptionType: NullReferenceException - Description: Processed data: [some][g:GROUP582]; Default type: All. - StackTrace: 2021-04-06 20:50:25.432: Processed data: [some][g:GROUP582]; Default type: All.. System.NullReferenceException: Object reference not set to an instance of an object.
at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
at Dynamicweb.Ecommerce.Extensibility.Controls.ProductsAndGroupsHandler.AddHandlerToCache(ProductsAndGroupsHandler handler, String handlerData)
at Dynamicweb.Ecommerce.Extensibility.Controls.ProductsAndGroupsHandler.ParseData(String data, Boolean loadDataFromDatabase, HandlerConfigurationType defaultDataType, List`1& productIdAndVariantIds, List`1& groupIds, HashSet`1& iQueries)
Regards.