Oh yes, there's so many things that you should do. This was only to grasp the code they were doing. You need a technical advisor who is on your side and can challenge the dev agency. You also need to strike a balance between giving them some slack and fighting to get a solid solution. We relied on the dev agency until we got the initial 2mln investment, afterwards we hired internal devs who took over. But if we scared them too much we might have compromised the investment.