Sorry but I couldn’t reproduce the issue you’re describing, I tried several orientations but the smallest cube always moves after landing on it from a side. A recorded video or a map file would help to see what’s wrong.
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The “Character Movement” node you have there is a standard CharacterMovementComponent, you have to convert it to NinjaCharacterMovementComponent first; mouse-drag from the blue pin of the node to anywhere, a pop-up appears, make sure the “Context Sensitive” checkbox is active, search for “ninja” and select the casting option; the result should be a valid Target for the “Set Fixed Gravity Direction” node.