Not sure, may be something related to the position or the direction vector you defined. I suggest simplifying your example and rule out the options one by one. Use monoenergetic distribution, then isotropic etc. Similarly then simplifying your /hist/point spectra. Also, one trick you may want to do is save the spectra in a separate file and call it in your mac. This will make your mac tidy; see here.
Also, what if you define the particle type, position, biasing in the same sequence as here? Does that change anything. There are examples in Book For Application Developers.