Later reports suggest that the building, erected on reclaimed land, was sinking. Too much movement and building envelope issues could have impacted the integrity on the structure. Also, if this was a post-tension roof, they should have used ground-penetrating radar before making any new cuts or cores, since it could compromise the integrity of the roof.
Buildings in Florida need to be recertification and inspected every 40 years; this one was due or undergoing its evaluation.
Cracks, no matter how minor, should be thoroughly inspected by a structural engineer.
Units sold in previous years were advertised for $650,000. (!).