I've been shopping for them for several years and have never had a problem getting paid. Does your shop log show your shop as approved and/or paid; maybe something has fallen through the cracks. Have you tried contacting someone at the company instead of going through the scheduler?
I don't think you're justified in telling shoppers to BEWARE due to one missing payment. I don't blame you for being upset about not being paid, but really, assuming or implying that this is typical for AI is unwarranted at this point. If they ultimately refuse to pay you for an accepted shop, then that's another thing....
I learn something new every day, but not everyday!
I've learned to never trust spell-check or my phone's auto-fill feature.