My DataStore Script Is Not 100% Reliable. Any Advice on the provided script?

This really worries me. lets pretend there is a cash value which saves/loads under my system. I had 42M cash and I lost it! It didn't save nor did the value re-load!

This is a super-simplified version of my data-store script to save you some time. Are there any faults in this script or any missing security? Thanks.

-- simplify the save process

local function saveData(key, saveData)
    DataStore:SetAsync(key, saveData) -- save the data
end

game.Players.PlayerAdded:connect(function(player)
    wait()

    local key = "Player_" .. player.UserId

    local plrData = DataStore:GetAsync(key) -- loading data

    spawn(function()
        while wait(60) and player.Parent == game.Players do
            --Save key: {kos, volume}
            saveData(key, {player.leaderstats.KOs.Value})--save the data

            if player == nil then
                break
            end
            print(player.Name .. "'s work was saved.")
        end
    end)

    if plrData then

        --Save format: {kos, volume}
        player.leaderstats.KOs.Value = plrData[1] or 0 -- data save
    else
        --######ey: {kos, volume}
        saveData(key, {player.leaderstats.KOs.Value})
end

game.Players.PlayerRemoving:connect(function(player)
    --Save key: {kos, volume}
    saveData("Player_" .. player.UserId, {player.leaderstats.KOs.Value}) -- save that data
end)