using "/replaceitem entity @a minecraft:potion 1 373 {CustomPotionEffects:[{Id:1,Amplifier:0,Duration:160}],display:{Name:Swiftness Potion}}" I got a potion with a missing texture, the same happened when I changed the effect to leaping, I may be doing something wrong, however I think this is likely a bug with the new format of potions
Potions do not use the Damage value anymore. Invalid Damage values will give the missing texture. Fixed command: