I change my player's character to a really small model and it's hard to move, how to fix this?

So I created a model, then I scale it down really small, when the character change to that model, it's really hard to move the character, here's the code I used to change the character:

local CharacterModel = game.ReplicatedStorage.CharacterModel:Clone()
CharacterModel.HumanoidRootPart.Anchored = false
CharacterModel.HumanoidRootPart.CanCollide = false
CharacterModel.Parent = workspace

CharacterModel:SetPrimaryPartCFrame(player.Character.PrimaryPart.CFrame)

player.Character = CharacterModel

Also, the HumanoidRootPart size is Vector3.new(0.505, 0.505, 0.252)

Are you trying to make it the starter character they spawn with?

If so, simply just add the model into StarterPlayer and name it StarterCharacter. It should then use it as the global starter character.

If this didnt help can you emphasise what your trying to do?

One of the reasons of this happening could be because the Walkspeed is either too high or too low for the model, try playing with that value of the humanoid and see if you change the movement of your character.