The DoD has very publicly stated that these are safe; I know Americans have a lot of distrust in their military but when it comes to matters of national security and defense the intel community is more or less omniscient.

Knowing the current capabilities of the military, there is also no possibility that this is not safe and yet cannot be handled after this long, which kinda rules out any boring explanation.

When it comes to matters of UFOs, drones, and lights in the sky, it has only ever been a boring explanation. I think people want very much for it to be fantastical, but often times the boring reality is still very dramatic if you step back and consider we're talking about secret testing of highly advanced drones.