That doesn’t match the problem I’ve had. I’m not at the bottom when it jumps back up. Usual case for me: scrolling lots of unread posts on my iPhone (Safari) in the morning, I’ll get through 20 of 50 unread posts, and it’ll suddenly jump back to the beginning of the 50 unread posts, where I’d started a minute or two earlier. And I’ll scroll down to try to figure out where I left off. And it may jump back up again.
EDIT: For what it’s worth, although I’d be seriously surprised if it matters at all, I often encounter a similar bug in Twitterrific.
mine too, except it is chrome on Android cell phone, and I’m scrolling up from newer to older, and it suddenly jump down to somewhere between I started and reached.