Do you have anything else happening in the double click actions list? Is your walk using the default sliding walk system or the update position on each frame system? If it's the latter then the speed thing shouldn't work for it.
Alternatively instead of using walk speed option you could try using my Lua script method if you want for changing the global delay values for each of the walk animations.
execute a script > if game.CurrentCharacter.CharacterScene == game.CurrentScene then
for i = 1, #game.CurrentCharacter.CharacterOutfits["default"].OutfitWalkAnimations do
game.CurrentCharacter.CharacterOutfits["default"].OutfitWalkAnimations[i].AnimationPause = 20
end
end
wait until character "current character" stops
execute a script >
for i = 1, #game.CurrentCharacter.CharacterOutfits["default"].OutfitWalkAnimations do
game.CurrentCharacter.CharacterOutfits["default"].OutfitWalkAnimations[i].AnimationPause = 40
end
I update the global delay on double click if the current character is on the current scene, then I wait until the character stops & then I reset the global delay back to the default value.