Diagnosis
A bearing in one of the cooling fans has failed or a foreign object is obstructing the fan blades. The Horizon Ultra uses a dual-fan system for the laser light source and main board.
How to Fix It
Power off and unplug the unit. Inspect all external intake and exhaust grilles for dust clumps or debris. Use a can of compressed air to blow out the vents from multiple angles. Do not insert tools into the vents. If the noise persists after cleaning, the fan assembly requires replacement.
If That Didn't Work
The noise indicates mechanical fan failure. This is not a user-serviceable part. You must contact XGIMI support for a warranty repair. Continued use with a faulty fan can lead to overheating and permanent damage to the laser diode or DLP chip.
Heads Up
Never operate the projector on its side or in a confined space. This disrupts the designed airflow path and can cause premature fan failure due to increased thermal load.