You speak about videos, sensors and tracking. But there are many cases over the past decades where radar records match what multiple eyewitnesses observed simultaneously: Physical objects performing maneuvers not possible with human technology.
Also, i would totally make contact with an industrial civilization that threaten to destroy most of its ecosystems before they do so, and if ET are visiting us, they are at the very least jerks. The "studying us" explanation doesn't fly, because if we are ever capable of navigating through the stars, we will be able to simulate false worlds with human who think they are biological and not simulations on them.
All I can say is, take a look at what the Navy is willing to publicly say about what they're working on:
https://www.nrl.navy.mil/Our-Work/Areas-of-Research/
https://www.nrl.navy.mil/tewd/
https://www.nrl.navy.mil/tewd/vrs/
Just because the Navy's camera man or the radar techs he talked to didn't know what they were, doesn't mean the captain of the ship didn't know what they were.
Unidentifizierte Flugobjekte über Europa. Wissenschaftliche Beweise durch Radargeräte, optische Sensoren und militärische Luftraumüberwachung. Mit 4 Tabellen und einem Katalog der über Deutschland gesichteten UFO-Formen. ISBN 10: 3776621109
You can do better than that, surely.
I referenced von Ludwiger's work because he is in possession of raw radar data, for example from Switzerland.
If you just want to scroll through a short selection of radar-visual cases, start here: http://www.ufoevidence.org/Cases/CaseView.asp?section=Radar&...