I haven't seen or heard of any problems, but you might try switching on the high security for each bill you take, or for whatever denomination you might be getting as counterfeit.
You may want to disable the $20'S for a month. I would hope you have cameras to help identify them. I am amazed the mars can be fooled. also i would like to know more if you are willing to share offline.
Mars was made aware years ago that their validators were excellent against stringing, but were susceptable to counterfeit. They were even given samples of bogus bills that could cheat their validators. I don't know if they ever did anything with this information.
Need more information. I have 12 Mars validators. Never once had this happen.
What denomination are you talking about?
How many did you get?
Did you report this to the Secret Service?
How did you know they were counterfeit?