Canadian embassy staff in Cuba still experiencing unexplained brain injuries

Canadian diplomats in Cuba are still experiencing bizarre unexplained mild brain injuries, and, following the latest victim on December 29th, the Canadian embassy in Havana has just halved its diplomatic staff there from 16 to 8, causing something of a diplomatic incident in the process.
Both the Canadian and American embassies in Havana have been reporting symptons of mild traumatic brain injuries (although without any actual trauma to explain them) since late 2016. Among the symptoms are headaches, nausea, dizziness and trouble concentrating, and the episodes were often associated with unexplained irritating sounds (crickets?), vibrations and feelings of pressure. There have been 26 cases reported among American embassy staff, and this last case brings the Canadian total to 14.
What's really weird is that, after all this time and despite working closely with the Cuban government to try to identify the cause of the injuries, neither country has any idea of what might be happening. Possibilities such as microwave assaults, sonic weapons, viruses, chemical agents, mass dlusions and malfunctioning surveillance equipment (my own personal favourite theory) have all been suggested, but the actual cause remains unknown.
Even weirder, since this last summer, American consulate staff in Guangzhou, China have been reporting very similar experiences, and several US diplomats, employees and their families have been evacuated and medically evaluated. Still no conclusions. Very strange.