The dogs may make mistakes, but the handlers don't. I've heard that a lot of dogs are trained to "hit" on subtle cues from their handler. So if they want an excuse to give you a hard time, the dog will "hit" on you or your car and out comes the Vaseline & gloves, and your car gets taken apart while you are detained. Later it will be determined the dog made a mistake...
There was a test done recently for 50 dogs, they brought them in to a room with NO DRUGS Anywhere, Every Last Dog Hit on something in the room because they didn’t want to FAIL the handler. All of this has been very well documented
And the first thing they are trained to hit on is MONEY... CASH...