This issue has been a pain since we started on version 4.9 and is still present in 4.13. In order to reproduce it, create a Cpp project and in code create a new component containing something similar to this:
UPROPERTY(EditAnywhere, Instanced, BlueprintReadWrite, Category = “ObjecsList”)
TArray ListOfObjects;
Now build and open the project in editor. Create a new blueprint actor and add this new component to it. Save, compile and add this new actor to the level. Select it and under Details panel find the TArray. If you try making any changes, array will instantly revert to whatever was set up in the blueprint,