You're sure you did it correctly? Select only the Vertex that is misbehaving then click on the Rel Roll button to change to turn that feature on for that Vertex. The roll will now start based on what the previous point was rolled at. For example if the previous point was banked at 30 degrees to the right, when set to 0 the next vertex with Rel Roll on would be at 30 degrees, or 0 change from the previous. If you waned it to be 45 you would change the roll to 15, 50 means to set the roll to 20, and so on.
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