Why wouldn't the first coroutine, Loop1, yield?

*Someone told me that you can use coroutines in order to prevent a glitch from happening. I tried it, and it still glitches.

I ran the server. The moving part successfully moved until five seconds. It blinked blue and orange.

This is the "before" of the script.*

while true do
    while true do
		script.Parent.CFrame=script.Parent.CFrame+Vector3.new(0,0,0.5)
		wait()
		script.Parent.BrickColor=BrickColor.new("Bright orange")
	end
	wait(5)
    while true do
		script.Parent.CFrame=script.Parent.CFrame+Vector3.new(0,0,-0.5)
		wait()
		script.Parent.BrickColor=BrickColor.new("Bright orange")
	end
	wait(5)
end

This is the "after" of the script when I converted the loops into coroutines.

local Loop1 = coroutine.create(function()
    while true do
		script.Parent.CFrame=script.Parent.CFrame+Vector3.new(0,0,0.5)
		script.Parent.BrickColor=BrickColor.new("Bright blue")
		wait()
	end
end)

local Loop2 = coroutine.create(function()
    while true do
		script.Parent.CFrame=script.Parent.CFrame-Vector3.new(0,0,0.5)
		script.Parent.BrickColor=BrickColor.new("Bright orange")
		wait()
	end
end)

while true do
	coroutine.resume(Loop1)
	coroutine.yield (Loop2)
	wait(5)
	coroutine.resume(Loop2)
	coroutine.yield (Loop1)
	wait(5)
end

What's wrong with the "after" code, and what can I do to fix the "before" code?

I would not suggest using coroutines for your script because they are unnecessary for what you are trying to do. I'm assuming that what you're trying to do is make each while loop run for 5 seconds, and then continue on to the next while loop. If that's true, then right away there are problems

First of all, you're using an infinite loop that will never break. If you want the loop to run for only a specific amount of time, I would suggest using either a for loop or using the tick() command. For our sake, we're going to be using the tick() method.

tick() is a command that will return the number of seconds that have passed since January 1st, 1970. It's that way because that's UNIX time (More info on UNIX time: UNIX).

We can use the tick() command to get the amount of time elapsed between 2 points in a script, or for many other applications. For our purpose, we're going to use it to tell when 5 seconds has elapsed since the start of the while loop.

In order to do that, we first have to define what the current time is before the loop starts, so we have an "origin" time, like so:

local Start = tick() --The variable "start" now contains the amount of seconds that have passed since January 1st, 1970

Now the second part is to check how much time has elapsed since the start, and in order to do that, we call the command a second time and subtract the 2 times to get how much time has passed in between them, like so:

local Start = tick()
while true do
	local Elapsed = tick() - Start --The variable "Elapsed" now contains the amount of seconds that have passed since the Start
	script.Parent.CFrame=script.Parent.CFrame+Vector3.new(0,0,0.5)
	script.Parent.BrickColor=BrickColor.new("Bright blue")
	wait()
end

Now that we can get how much time the loop has been running for, we need a way to break the loop after it's been running for 5 seconds. We use the break command for that. The break command is used to exit any running loop and continue with the thread. We can use it like so:

local Start = tick()
while true do
	local Elapsed = tick() - Start
	if Elapsed >= 5 then --If the elapsed time is greater than or equal to 5 seconds...
		break --break out of the loop and continue with the thread
	end
	script.Parent.CFrame=script.Parent.CFrame+Vector3.new(0,0,0.5)
	script.Parent.BrickColor=BrickColor.new("Bright blue")
	wait()
end

Now that you know how to make the first while loop run for 5 seconds, you can use the same method for the rest of your loops. Hope this helped!