Sorry to hear about Dozer
It does sound like Bear could be having a seizure of some sort, cb3228. Do you have a video camera? If you can catch an episode on video to show your vet it might help in diagnosis. I think you're right--vestibular syndrome tends to linger and improve with time.
I hope you figure out what's going on with your youngster soon, cb!
(And if you get a chance, we'd love to ooo and ahhhh over your furbabies if you have some pics to share!