Diagnosis
This is almost always caused by IR light reflecting back into the lens from a nearby surface or from dirt on the camera dome. The TrackMix's IR LEDs are powerful, and reflection causes "IR bloom."
How to Fix It
First, clean the camera's clear plastic dome with a microfiber cloth and a tiny bit of glass cleaner. Fingerprints or condensation cause major blur. Next, look at what's near the camera. Is it mounted under a soffit or too close to a wall? The IR lights hit that surface and bounce back. Angle the camera slightly downward so the IR illuminates the ground, not the wall behind it. You can also try reducing the IR intensity in Settings > Display > IR Light.
If That Didn't Work
Check the video settings. In Display settings, ensure "Night Vision" is set to "Auto" (not forced to Color or Black & White). Also, the 4K wide lens has a fixed aperture, so in pitch black, some grain is normal. If it's truly foggy, moisture might have gotten inside the sealed unit, which is a warranty issue.
Heads Up
Spiders love to build webs directly over the IR LEDs and the dome because insects are attracted to the IR light. A single web strand right on the dome will create a massive, blurry flare in the night image. Check for webs frequently.