Why is there water vapor in the middle of the double glazing and how to solve this problem?

The double glazing is composed of two or more pieces of glass sandwiched with aluminum spacers. The aluminum spacers are made of molecular sieves and the outer edges are sealed with a sealant. If it is not sealed at the time of manufacture, or if the molecular sieve is missing, the phenomenon of water vapor will occur, and it will not be wiped off when the glass is wiped off. But when the weather warms up, the fog will naturally disappear, and it will be cold. Will appear again. If it enters the dust, it will have a great impact on its lighting and aesthetics. What if there is water vapor in the middle of the double glazing?