Tenant oplog applier takes care of updating the session entry in the config.transactions table for those donor transactions that are committed after startApplyingDonorOpTime and this pre-oplog catchup step takes care of updating the session entry in the config.transactions table for those donor transactions that are committed before startFetchingDonorOpTime. But, misses updating the config.transactions table for those donor transactions that are committed in this range [startFetchingDonorOpTime, startApplyingDonorOpTime] where startFetchingDonorOpTime <= startApplyingDonorOpTime. This can lead to duplicate transaction commits.