[dchan]

Since this is an issue regarding the diagnosis and correction engineering flaws in a building structure, the most likely route towards correcting the problem would be via a forensic engineering investigation. Most municipal building inspectors are trained only in pointing out quantitative flaws based on building codes (such as noting inadequate fireproofing, emergency lighting, etc.) from their rather brief visits to a building, so they wouldn't be the ones to carry out the investigation. It would most likely be done either by a private consulting firm, or by the firm(s) that did the original engineering and design for the building.

I think you answered the question yourself - the problem could be due to excessive building structural flex*, or it could be due to improper window anchorage design or installation, or it could be something else. But you can't say for sure which is the major problem that needs to be addressed until you make a thorough investigation of the building under wind conditions.



* For skyscrapers, whose primary lateral forces are due to winds, some degree of structural flex is necessary. But modern engineers try to avoid the difficulties in designing a building structure to withstand high wind loads by aerodynamically designing the building to simply avoid the winds, and therefore, relax the wind load requirements on the structure. This was done for the Burj Khalifa tower by designing the building so that its floor area becomes gradually smaller as it goes higher, as well as by the design of the setbacks. I believe the design of the setbacks allowed for the winds to circulate counterclockwise or clockwise around the building. Don't remember which.