so you probably have a partial short across 5v somewhere, something pulling too much amps and hitting thermal throttling of the voltage regulator. If you have anything plugged in unplug it and confirm that the voltage stays at 2.4. Then you’d have to start looking at things on the unity to see where the short is occuring, luckily not too much stuff sits on the 5v bus.
My first step would be to de-pop the 3v3 regulator and confirm that 5v line stays low at 2.4v:
It’s super big and easy to lift off if you have a hot air gun. If you don’t have hot air gun just lifting up this first leg in green will disconnect 5v from the regulator.
If 5v stays low then its something on 5v bus if it goes back to normal its something on 3v3.