Simple set up. Opened up swamp preset and did the following:
Collider to prim shape ( box).
Dropped box through Z space with 2 key frames (30 to -30).
Works as expected.
Collider to prim shape (torus).
Dropped box through Z space with 2 key frames (30 to -30).
Works as expected.
Collider to shape blend. Shape A (box). Shape B (torus).
All key frames the same.
Collider moves through space as keyframed - no interaction with environment.
Tested multiple iterations. Zero collisions detected. Tested every blend option type - none worked.
Screenshots to follow.