Yes, there are very good instances of radar tracking. One was quite a sensation since the FAA head even brought the tapes forward after the CIA thought it had taken the originals ... they collected copies not realizing or even asking the FAA director if the ones they confiscated were the only copies. That particular incident happened to a Japanese airline pilot and his sighting, which was well documented with radar imagery and the actually recordings between ground and the pilot.
And what about the ones that do not show up on radar?
Rendlesham was all visual sighting with no radar confirmation.