Is it true: Havana Syndrome?

It's still under investigation.

The 2020 National Academies of Sciences report concluded that "directed, pulsed radio frequency energy appears to be the most plausible mechanism in explaining these cases" among those it considered, while saying it could not rule out other mechanisms. US intelligence assessments later pointed the other way: in March 2023 the Director of National Intelligence said most intelligence agencies had concluded it was "very unlikely" a foreign adversary was responsible, and AP reported that a January 2025 update had five of seven agencies reaching the same view while two took a more open view with low confidence. In June 2026 the Director of National Intelligence rescinded both assessments, and CNN reported in January 2026 that the Pentagon had been testing a device bought in an undercover operation that some investigators think could be the cause; its link to the incidents is debated. A March 2024 NIH imaging study found no significant evidence of MRI-detectable brain injury, and 2024 reporting by The Insider, Der Spiegel and 60 Minutes linked Russia's GRU Unit 29155 to some incidents. The case is genuinely unsettled: symptoms are real, cases are documented, mechanism remains contested.