I also think that some sort of embassy-operated anti-eavesdropping emitters being the cause is the most plausible explanation. Embassies are typically espionag

I also think that some sort of embassy-operated anti-eavesdropping emitters being the cause is the most plausible explanation. Embassies are typically espionage stations, i.e. they're almost certainly full of equipment that monitors every measurable aspect of the EM spectrum and probably various other things too. Covertly deploying any kind of electromagnetic weapon near an embassy sounds like an impossibility to me. But if the embassy's own security hardware caused it, it's very likely that it would be kept secret (also to protect the secrecy around such hardware). It would also explain why it happened in multiple locations.