IList's are a bit quirky compared to some other fields. They have a few issues and were mainly made for simple lists so it doesn't surprise me.
You can disable features for Content areas, like the create link so it becomes just a droppable area, that may work for you.
I have a simple content reference list for images defined as below:
For some reason on-page editing only allows me to drop one image at a time on this property. The moment I select more than one, it does not allow drop anymore. The drop area disappears. The only way I can drop multiple is if I click on the edit area and the editor pops up, that does allow multi-drop. Its quite annoying to my editors.
This does work however for a ContentArea property. I tested with both but I dont want all the extra features ContentArea brings with it. Any ideas on what I can do to improve this experience? Is this a known issue?