Who should pay for the bugs?

[Syndicated Puzzles]

We contracted a build outside of iLifeTouch. Going well except for bugs.

Now here is a general question. At what point should the dev fix the bugs without demanding to get paid for work that was supposed to be working in the first place. We complained to the programmer but he insisted it was part of the process. This is the fourth update and I fear new bugs will appear mysteriously again.