When migrating a struct with a soft reference from 4.17 (or older) to a newer version of the engine, the soft reference will have it's default value converted to an integer after a new member variable is added to the struct.
Result: The soft object references are changed to integers (in the default values panel)
Expected: The soft references would remain soft references
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-55783 in the post.