Sealed Units can blow quickly, especially when fitted badly, some cowboys knock the units in with hammers, which split the mastic seals.
Moisture will begin to build up within the units, and when we come along and clean the glass with cold water, it causes the moisture within the units, to condense on the internal surfaces. Thus making it appear that it is our water that has leaked into the units.
I once had an irate customer accusing me of breaking his sealed units, and I had to explain this to him, he went away muttering that he had friends in the industry and he would check up, well I still do his windows several years later !