Rest API: Reindex Progress in Jira Datacenter

Hi all,

having a data center jira installation we trigger background reindex via this REST API:

Once reindex is triggered, we can check progress using this endpoint:

Sometimes, the progress endpoint returns data of a previous reindex operation.

I just called POST to reindex, getting this response:
“progressUrl”: “/secure/admin/jira/IndexProgress.jspa?taskId=12511”,
“currentProgress”: 16,
“currentSubTask”: “Currently working on: Issue index”,
“type”: “BACKGROUND”,
“submittedTime”: “2019-02-27T14:21:13.054+0000”,
“startTime”: “2019-02-27T14:21:13.067+0000”,
“success”: false

So reindex is already running and the start time is 02-27 at 14:21.

Few seconds later, I check for progress and I get this result:
“progressUrl”: “/secure/admin/jira/IndexProgress.jspa?taskId=12611”,
“currentProgress”: 100,
“type”: “BACKGROUND”,
“submittedTime”: “2019-02-27T12:56:52.690+0000”,
“startTime”: “2019-02-27T12:56:52.699+0000”,
“finishTime”: “2019-02-27T12:58:30.985+0000”,
“success”: true

So I received data for a previous task that already finished 12:58 on the same day.

My expectation would be that /progress always returns the data for the most recent task.
As from the documentation:
“If a reindex is currently taking place then information about this reindex is returned.”

Sometimes it does that, but sometimes it also returns data from a previously completed task.

Is the API bugged or am I doing something wrong?