my guess is that the outdoor AC unit reached its maximum working temperature...

since we're not that used to extreme heat in EU, units with max working temperatures of 45 degrees Celsius are pretty common and the air around the AC unit is warmer than regular outdoors air, doubly so if they're placed on the ground and the glass from the building reflects some additional heat from the sun.

the risk of this was broadcasted in our local news for home AC owners when the forecast reached 40, as lots of apartments have the AC on partly glass-encased balconies, or on walls facing direct sunlight...