I created a document type which contains a Member Picker property. Accessing the (IPublishedContent) value of this property in code is very slow, even when just checking whether the referenced member is set (by doing a null check). This becomes especially noticeable when looping through multiple items: evaluating ~1100 items takes about 12 seconds.

Therefore I attached DotTrace to my running instance and it seems that the member cache is not being hit. Does anyone know what might cause this behavior and how to improve performance?