Opposing counsel's client keeps contacting me and my clients

What's the best way to approach the other side? Awaiting for a hearing, but OC's is impatient and regularly goes rogue and sends emails directly to my client and me (or copies me, their client and their own counsel), sometimes stating illegal things they plan to do.

When it first happened, I asked OC to confirm they were still representing the client. They said yes. I have asked OC a couple times to keep communication between representatives but this problem is ongoing. Interested in hearing how others have handled situations like this.