In WT-3181, specifically: https://github.com/wiredtiger/wiredtiger/pull/3373/files#diff-a6c8d99189e5865e35b893d6792f1165L694 – the logic around updating btree->rec_max_txn was unintentionally flipped. This can lead to clean pages being evicted when they contain updates that could be required by queries.