Hi there, this is a known issue due to how the gun worked when it was originally released. When originally released, the gun would drop at max light, no matter how low your light level was, and Bungie made it non-infusable so you couldn't just move the light level to another gun. However, since then, they never changed it so it could be infused. Check the @BungieHelp Twitter and future This Week at Bungie posts occasionally for possible changes on this situation.