Hi Both,
What you show Thomas is also what I obtain when I run a 241Am isotope source and measure the radiation product yield out of the semi-analogue decay.
You can indeed see the 241Am decay products (59keV gamma, 13.9 keV XR, etc.), however, keep in mind that 237Np, the daughter of 241Am is itself unstable (and so on), and you will proceed down the whole decay chain until you reach stability, thereby emitting decay products from a series of nuclides, not just the ones directly coming from the alpha decay of 241Am. I should note that this is perfectly expected behaviour as the semi-analogue mode gives products integrated over infinite time.
The three other cases you investigated, Tim, are all decaying directly to a stable nuclide, reason why you did not have the same issue arising there.
We also checked the FLUKA radiation product database, and I can report that we do not see any issue with any of the isotopes involved in that decay chain.
Cheers, hope that clears things out
Philippe