I'll keep this simple. They are very late completing payroll.
Not only is this with me, but also with others I work with that are employed contractually by Aerotek. At one point they were over 5 figures behind in payments to me. There is always an excuse or promise of new policies being put into effect, but never any improvement.
You can choose to believe me or not, and frankly, having a job is most important, but plan on spending a lot of time and effort getting your paychecks from them. Especially your final paycheck(s). I wish you the best of luck.