Currently the following scenario is possible within wired tiger

self.conn.set_timestamp('stable_timestamp=6');
session1.begin_transaction()

session1.timestamp_transaction('commit_timestamp=7')

self.conn.set_timestamp('stable_timestamp=8')

cur1[1] = 4

session1.commit_transaction()

This presents an issue as if we check pointed at stable timestamp 8 we couldn't guarantee what would be part of the checkpoint.