Problems caused by imperfect junctions
Usually the cable that comes from the technical room, before reaching the niche (A), is interrupted inside a junction box (B). Unfortunately, experience shows that these junction boxes are often not watertight and fill up with water or moisture. In this situation, if the junctions between the two cables (incoming from the technical room and outgoing to the lamp) are not watertight, there is a danger of water entering the lamp through the cable.
While it might seem impossible to explain the phenomenon, it is actually very simple. The lamp is a body built with a rate of protection IP68; this has to guarantee operation in an underwater environment. Normal operation involves a continuous succession of switching on and off. Every time the lamp is switched on, the temperature inside the lamp increases due to the presence of LEDs (each LED gives off heat during operation). The immediate consequence is an increase in internal pressure. When the lamp is switched off, the opposite happens, i.e. a decrease in the internal temperature with a consequent decrease in pressure.
Since the body is watertight, this creates a "pump effect". It is easy to see how, in this situation, humidity and water easily get inside the lamp, if the junctions made in the junction box were not watertight. The amount of water that could enter the lamp obviously depends on various aspects (number of times the lamp is switched on/off, difference in level between the junction and the niche).
This makes it impossible to estimate the time it will take for the water to get inside the lamp. What we are certain of, however, is that, once reached, the situation could degenerate in a very short time because the simple contact between water and electronic components would irreversibly damage the latter and the lamp would most likely be beyond repair.