Indeed. Realistically, we have no idea how they spawn or if there's any more to it than simple blind luck even. People hunting UA convody went weeks without finding anything, so I think it's premature to think it's bugged simply because we didn't find them after a day of searching.
Scuttlebutt said someone actually saw an Unknown Probe in the cargohold of a ship in a convoy a fair few weeks back, but they neither had proof nor seemed to be concerned with trying to find it again. Could very well be like the guy who initially posted this
fake video, and then followed up with
this video of the UA which by all accounts is actually legit footage well before the first verified UA find. Other people had produced fake videos of UAs using "means" but couldn't actually do it correctly. Meanwhile that one does seem legit, though nobody believed the guy due to his first fake video (boy who cried wolf).
tl;dr people are almost definitely happening upon these accidentally, and they're likely random, very rare spawns. By searching Ross 47 based on one report it's just more confirmation bias that "That's where they spawn" when realistically, you might go days without seeing a spawn, and it might not matter where you are searching.