I first noticed this with my K-Drive. I've reached Bondi rank 1 several times on the Vallis, but I've just done a Uranus submersible mission, which distinctly told me my Itzal was rank 29 in its midst. When it came to the completion summary, neither that Archwing, nor any of its weapons were listed, and upon investigation, Itzal has regressed back to rank 28.