I was playing a nightfall where the loadout is locked and noticed that my pure poetry wasn't working so I ended up testing every gun I owned with the osmosis perk and found that only Pure poetry was unable to change damage types. For the record the guns I tested were: Firefright (enhanced), Boudica-C, Escape Velocity, Battle Scar, Fortissimo-11, Traveler's Chosen, and Chain of Command, and Pure Poetry. I was unable to determine what might have been the cause of this but Osmosis is one of my favorite perks and I hope this can be fixed soon.