3.0 and native protocol V4 introduced a change to how PagingState is serialized. Unfortunately that can break requests during upgrades: since paging states are opaque, it's possible for a client to receive a paging state encoded as V3 on a 2.1 node, and then send it to a 3.0 node on a V4 session. The version of the current session will be used to deserialize the paging state, instead of the actual version used to serialize it, and the request will fail.
This is obviously sub-optimal, but also avoidable. This JIRA fixes one half of the problem: 3.0 failing to deserialize 'mislabeled' paging states. We can do this by inspecting the byte buffer to verify if it's been indeed serialized with the protocol version used by the session, and if not, use the other method of deserialization.
It should be noted that we list this as a 'known limitation' somewhere, but really this is an upgrade-blocking bug for some users of C*.