Why is the fluence suddenly dropped, is it because of Ny size in scoring?

[ceruttif (Francesco Cerutti)]

Since your beam is not pencil-like, but has a transverse size and a divergence, in order to change its direction you have to use BEAMAXES and not BEAMPOS.

@cesc

To make the BEAM card parameters apply to a custom beam direction [i.e., different from the z-axis] you should use the BEAMAXES card.