Mixing tweens with animations doesn't seem to work well... Did I do something wrong, or was it just a bad idea?

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This script uses tween service to slowly rotate a coin.

--this script is gonna animate the power up and make it spin and oooooooooooooooooooooo pretty


local tweenService = game:GetService("TweenService")



--creating rotationTween
local rotationTweenInfo = TweenInfo.new(
	5, -- Time
	Enum.EasingStyle.Linear, -- EasingStyle
	Enum.EasingDirection.Out, -- EasingDirection
	-1, -- RepeatCount (when less than zero the tween will loop indefinitely)
	false, -- Reverses (tween will reverse once reaching it's goal)
	0 -- DelayTime
)

local rotationGoal = {}
rotationGoal.Orientation = Vector3.new(0, 360, 0)

local rotationTween = tweenService:Create(script.Parent, rotationTweenInfo, rotationGoal)



--main script
rotationTween:Play()

This script makes it float up and down with an animation.

--this script plays the float animation with the animation controller


local animation = Instance.new("Animation")
animation.AnimationId = "rbxassetid://8689943119"

local loadAnimation = script.Parent.AnimationController.Animator:LoadAnimation(animation)
loadAnimation:Play()

Individually, they work fine, but together, the rotating seems to work, but it flies upwards into the heavens. The animation makes it go up .5 studs for 1 second, and down .5 studs for 1 second. It seems to go down .5 studs for 1 second, but when it goes up it goes like 50 studs for 1 second, then repeat both of those.
What on Earth is going wrong?