I have worked for AQ. There pay period is much longer than other companies. In fact the longest in all the companies I registered with. Before my first shop I was skeptical about them. I asked for advise here and the best one was, "while they are a legit company, go with your gut".
I did, and finished one shop for them. Took me a very long time to get paid. Like the OP said, different excuses such as profile not being updated etc. I kept sending emails was paid my 5 bucks but it took me efforts worth 50 bucks to get what I was owed.
However, for a few subsequent shops the paid came in on time. I did reach out to my scheduler before the due date.
More recently I did some shops in nov and was not paid and realized that I wasn't paid. I sent an email to the scheduler and was being tossed around because the scheduler had left the company.
I stood my ground and kept bothering them. Finally, I got in touch with a different scheduler (whose shops I got paid for on time) and she got me paid.
So, like the OP said, there definitely is a problem. However, in the end I was paid for all my shops.