Drag and drop to replace animation only works on certain samples in Blendspace

In a blend graph, the user can only use drag and drop to replace certain samples.

1. Open QAGame in editor.
2. Open the Blendspace TEST_Blend2D.
3. Drag an animation sequence from the Asset Browser across several different sample points in the blend graph.

RESULT

Only certain samples can be replaced. Attempting to replace on the others results in a dupe sample point being added.