You can reproduce this pretty easily, just create a new revision using arc diff and you should find a corresponding error logged on a taskmaster:
[2016-01-25 00:02:22] EXCEPTION: (PhutilProxyException) Permanent failure while executing Task ID 320. {>} (PhabricatorWorkerPermanentFailureException) Unable to load transactions: PHID-XACT-DREV-nhexnck64mngrhz. at [<phabricator>/src/applications/transactions/worker/PhabricatorApplicationTransactionPublishWorker.php:112]
arcanist(head=master, ref.master=b87138356a9c), phabricator(head=master, ref.master=a9e2e6c5aab9), phutil(head=master, ref.master=f43291e99d36)
#0 <#2> PhabricatorApplicationTransactionPublishWorker::loadTransactions(DifferentialDiff) called at [<phabricator>/src/applications/transactions/worker/PhabricatorApplicationTransactionPublishWorker.php:19]
#1 <#2> PhabricatorApplicationTransactionPublishWorker::doWork() called at [<phabricator>/src/infrastructure/daemon/workers/PhabricatorWorker.php:122]
#2 <#2> PhabricatorWorker::executeTask() called at [<phabricator>/src/infrastructure/daemon/workers/storage/PhabricatorWorkerActiveTask.php:171]
#3 <#2> PhabricatorWorkerActiveTask::executeTask() called at [<phabricator>/src/infrastructure/daemon/workers/PhabricatorTaskmasterDaemon.php:22]
#4 PhabricatorTaskmasterDaemon::run() called at [<phutil>/src/daemon/PhutilDaemon.php:183]
#5 PhutilDaemon::execute() called at [<phutil>/scripts/daemon/exec/exec_daemon.php:125]Underlying issue here is that the transaction is saved as a DifferentialTransaction rather than a DifferentialDiffTransaction.
mysql> select * from differential_transaction where phid = 'PHID-XACT-DREV-nhexnck64mngrhz'\G
*************************** 1. row ***************************
id: 15
phid: PHID-XACT-DREV-nhexnck64mngrhz
authorPHID: PHID-USER-rihx4366f3aczsvc2wtb
objectPHID: PHID-DIFF-fgt7avmnvsxgcbgzx5ci
viewPolicy: public
editPolicy: PHID-USER-rihx4366f3aczsvc2wtb
commentPHID: NULL
commentVersion: 0
transactionType: differential:diff:create
oldValue: null
newValue: true
contentSource: {"source":"conduit","params":[]}
metadata: []
dateCreated: 1453698141
dateModified: 1453698141
1 row in set (0.00 sec)