On the old server we had the offset at 0.
-1 was one of the settings I tried that didn't appear to solve the problem. I didn't wait for posts to be made after the change to -1, though, just checked by looking at posts made earlier that I hadn't yet read. Occurs to me now that perhaps that wasn't a good test; do I need to wait for posts made under the new offset? If so I'll try it again before opening a support ticket.
