[2020] Valence fusion destroys the extra weapon without giving any bonus effects to the original

Was this still the case after you relogged? Could you please check again?  Looking in your account I see that you fused a Kuva Bramma, it has bonus Heat damage, and the Heat value is higher than it was when you removed the weapon from the foundry. The bonuses appear to be valid, it might just not have showed up right away with the specific way you fused them?  (Which would still be a bug, but a less serious one)