Diagnosis
Normal operation. The internal amplifiers and processors generate significant heat during high-bandwidth tasks. The aluminum chassis acts as a heatsink.
How to Fix It
Ensure proper ventilation. Do not place the unit on plush carpet, inside an enclosed cabinet, or on top of other electronics that also generate heat. Place it on a hard, flat surface. Leave at least 2 inches of clearance on all sides.
If That Didn't Work
Feel the power adapter. If the adapter is excessively hot, not just warm, it may be faulty. A failing adapter can cause the unit to overwork and overheat. Replace it with the official TP-Link 12V/2A adapter.
Heads Up
Heat is expected, but burning smells, audible sizzling, or plastic deformation are not. In those cases, immediately unplug the unit and contact TP-Link support. Do not continue using it.