Removed adding compositions from parents as this breaks core functionality.

Ignoring property in mappings where it isnt needed.
Updating the LockedCompositionsResolver to get parent and use path instead of trying to use path which can be null on GetEmpty.

src/Umbraco.Core/Models/ContentTypeCompositionBase.cs

@@ -102,11 +102,6 @@ namespace Umbraco.Core.Models
                     throw new InvalidCompositionException(Alias, contentType.Alias, conflictingPropertyTypeAliases.ToArray());
 
                 _contentTypeComposition.Add(contentType);
-                //Make sure to include the composition's compositions since this is possible with inheritance
-                foreach (var contentTypeComposition in contentType.ContentTypeComposition)
-                {
-                    _contentTypeComposition.Add(contentTypeComposition);
-                }
                 OnPropertyChanged(ContentTypeCompositionSelector);
                 return true;
             }