That’s correct. Unreal sometimes chokes on custom structs for weird reasons. Save the struct (even though you haven’t done anything with it) and correct those graphs so that they look like this:
https://c2.staticflickr.com/2/1570/24099949132_15511b4711_o.png
https://c2.staticflickr.com/2/1569/24181890276_6b83570ac7_o.png