1) Remove my.polygon = on in the dummy action. This flag should only be set for non-moving entities, so just put it in the structure model action;

2)

Quote:

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POLYGON
If this flag is set, the model entity's real shape is used for OBB collision detection. Otherwise, an oriented bounding box or ellipsoid is used.

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So, you´d better try using c_move with OBB system. Also, check if you are not overriding the polycollision system somewhere. By default var enable_polycollision should be 1;