SERVER-42251 added code of using the prepareTimestamp to timestamp the multi-key write when reconstructing prepared transactions. SERVER-49949 did a fix to use max(prepareTS, oldestTS). But WT doesn't allow writing with timestamp < stable timestamp. And in the case when both the prepareTS and the oldest are < the stable timestamp, e.g. after rollback, we could violate the WT rule. To fix this, I think we should use max(prepareTS, stableTS).