Hey there, are you talking about the Scout Rifle, 'Wicked Implement'? It has Slow, making it an anti-overload weapon, so it is intentional. When a weapon has an anti-champion effect, or a keyword ability that is effective against a champion type, it means the weapon cannot gain the effect of an anti-champion mod. So in this case being anti-overload due to Slow means Wicked Implement cannot gain the effect of Anti-Barrier Scout Rifle, etc.