Is it possible scale physics nodes (or the underlying Mesh) by a negative number??
It seems that the volume becomes zero and no collisions will fire if the mesh itself is scaled by a negative number.
When the Physics node is scaled by a negative number this exception is thrown
java.lang.IllegalArgumentException: scale must not have 0 as a component!
Scaling by a negative number is a pretty powerful technique to mirror the geometry that I assumed would be supported by the ODE also.