Any way to save a array with DataStore without it erroring?

So i have a table that has... more tables and I want to save them. Here is the script:

game.ReplicatedStorage.SaveBuild.OnServerEvent:Connect(function(player)
    local partTable = {}
    
    for i, inst in pairs(workspace:GetChildren()) do
        if inst.Name == "BuiltBlock" then
            local position = {
                X = inst.Position.X,
                Y = inst.Position.Y,
                Z = inst.Position.Z
                
            }
            local material = inst.Material
            local color = inst.BrickColor
            local size = inst.Size
            partTable[i] = {Position = position, Material = tostring(material), Color = tostring(color), Size = tostring(size)} --array for each block
        end
    end
    
    local success, err = pcall(function()
        BuildsDataStore:SetAsync(player.UserId, partTable) --errors here
    end)
    
    if success then
        print("Saved player build.")
    elseif not success and err then
        print("Not successful: "..err)
    end 
end)

So, when I try to save it, it just straight up errors. Any help on this?