"Hey, Dave, do me a favor - tell your team not to tell Customers that they can X if they have a Y."
"Who told a Customer that?"
"I don't want to say; I don't want to get anyone in trouble."
"Okay. Can you give me the Customer's name? I can work backwards from that."
"Can't you just send around an email or something?"
No. No, no, no.
First, because if that actually worked, they would have gotten it right to start with. Second, it's clear that only one person is getting it wrong. Why waste the time of team members who already get it right? Are we deliberately trying to kill their morale?
There are a lot of things wrong with our current Avoidance Culture, and one of the worst is not trying to correct a problem at its source. If anything less than the entire team is getting something wrong, it's an abdication of your responsibility as their manager if you don't sit them down, face to face, and say: "This is something that you need to correct."
"But it's hard!" you cry. "I don't want to hurt their feelings!"
How will they feel when their bad habits accumulate to the point that you have to let them go, when you've given them no indication that they were doing anything wrong? Is that fair? Is it right? And how will your HR staff feel when that dismissed employee turns around and litigates? As far as they knew, everything was peachy.
If there is an issue, it's your job to coach your employee regarding how to correct it. Yes, they still have to do the heavy lifting, but you're not doing your job if you don't even tell them where the log jam is.