Run Animation Overriding All Others

So I have finally finished my movement system for my game but found that my running animation is overriding everything else when it’s being played. I also put my code here just incase the code is messing something up. Inform me if you figured out what’s wrong because it is really messing it up.

local UIS = game:GetService('UserInputService')
local Player = game.Players.LocalPlayer
local Character = Player.Character

UIS.InputBegan:connect(function(input)
	if input.KeyCode == Enum.KeyCode.LeftShift then
		Character.Humanoid.WalkSpeed = 35  --run speed
		local Anim = Instance.new('Animation')
		Anim.AnimationId = 'rbxassetid://15564406328'
		PlayAnim = Character.Humanoid:LoadAnimation(Anim)
		PlayAnim:Play()
	end
end)

UIS.InputEnded:connect(function(input)
	if input.KeyCode == Enum.KeyCode.LeftShift then
		Character.Humanoid.WalkSpeed = 16  --default walk speed
		PlayAnim:Stop()
	end
end)