This issue is not always reproducible but happens very frequently:

1. I built a web service to update maniphest status when received an event indicating the maniphest has been moved to a specific column in a project dashboard (this is done through feed.http-hooks)
2. what the service does is to call maniphest.update conduit api to update the task status
3. sometimes even though the conduit api call maniphest.update returns success, the actual maniphest task status is actually not updated

here is an example, I got the following response (based on the log of my own web service calling maniphest.update):

"result": {
    "id": "12396",
    "phid": "PHID-TASK-xtdqfvlmgyzszqoidfrt",
    "authorPHID": "PHID-USER-infd7ym6jl22imzdxj2l",
    "ownerPHID": "PHID-USER-infd7ym6jl22imzdxj2l",
    "ccPHIDs": ["PHID-USER-cmqw5rasptj2jwg7gakk", "PHID-USER-infd7ym6jl22imzdxj2l"],
    "status": "accepted",
    "statusName": "Accepted",
    "isClosed": true,

...

But when I call maniphest.query to verify the status of the task, it returns:

"PHID-TASK-xtdqfvlmgyzszqoidfrt": {
  "id": "12396",
  "phid": "PHID-TASK-xtdqfvlmgyzszqoidfrt",
  "authorPHID": "PHID-USER-infd7ym6jl22imzdxj2l",
  "ownerPHID": "PHID-USER-infd7ym6jl22imzdxj2l",
  "ccPHIDs": [
    "PHID-USER-cmqw5rasptj2jwg7gakk",
    "PHID-USER-infd7ym6jl22imzdxj2l"
  ],
  "status": "open",
  "statusName": "Open",
  "isClosed": false,

...

Another thing that is weird is that it will generate a feed indicating the task has been closed:

But in the maniphest view, the task status is still open:

Version:
phabricator 2c67d9c8ace2800ec618549963c4036e92cb3a9b (Mar 4 2016)
arcanist ccbaee585e1a350d1ff970c30481079dc8471a7c (Mar 7 2016)
phutil d20d6e725037538221b42a74b6dcb7a006834a7a (Mar 13 2016)