Diagnosis
Yeah, this one's common. That's the sound of the internal thermostat cycling the heating element on and off to maintain the set temperature. It's a mechanical relay, and it's normal operation.
How to Fix It
No fix needed—it's supposed to do that. The Vortex Plus uses a simple on/off (bang-bang) controller, not a smoother proportional controller. You'll hear a distinct "click" when it turns the heat on, and another "click" when it turns it off. The frequency increases during initial preheat and decreases once the target temp is stable.
If That Didn't Work
If the clicking is constant, rapid, and non-stop (like a machine gun), or accompanied by the unit powering off, that's a fault. Unplug it and contact Instant Pot support.
Heads Up
The noise is more noticeable on certain functions like "Bake" or "Roast" which cycle more frequently. "Air Fry" mode might hold a more consistent heat with slightly less frequent clicks.