My tweens are being faulty, why?

I've been noticing something very odd recently. Sometimes my ui won't tween. There are no errors in the game console, and when I rejoin something else won't tween or it's magically fixed! I have no idea what's causing this issue. I have checked the properties of the frames I'm tweening - they're normal.

Here is my code:

function beginWrittenResponse()
    for i=1, #writtenAnswer do
        local Answered = false
        Write.A.Text = writtenAnswer[i].A
        Write.B.Text = writtenAnswer[i].B
        Write.C.Text = writtenAnswer[i].C
        Write.D.Text = writtenAnswer[i].D
        Write.Question.Text = writtenAnswer[i].Inst
        Write.Visible = true
        Write:TweenPosition(UDim2.new(0,0,0,0), "In", "Sine", 1)
        coroutine.resume(coroutine.create(function()
            Write.Submit.MouseButton1Click:wait()
            if Write.TextBox.Text == "" then
                Write.TextBox.Text = "Please enter a valid answer!"
                wait(3)
                Write.TextBox.Text = ""
                return
            end
            Answered = true
            if writtenAnswer[i].Answer == Write.TextBox.Text then
                Score = Score + 1
            end
        end))
        repeat wait() until Answered
        Write:TweenPosition(UDim2.new(-1,0,0,0), "Out", "Sine", 1)
        wait(1)
        Write.TextBox.Text = ""
        Write.Visible = false
    end
end

Thanks in advance!