OBJECT CHANGE TRACKING, Execution status FAILED, category=internal error='.reqcache'

[#1]

Our grid is running v8.2.1-35966.  I have grid masters geographically dispersed with one HA pair at one location and a single server at the other.  Currently the single server is the grid master and the HA pair is the grid master candidate.

I have enabled Object Change Tracking (OCT) as documented in the NIOS Administation guide.  My OCT settings are set to the maximum of 7 days and 20000 records.  When I make API calls as documented the synchronization is scheduled, but ultimately fails.

INPUT
curl -k -E ./apilogin.crt.pem --key apilogin.key.pem -X POST 'https://10.0.0.1/wapi/v2.7/fileop?_function=read&_schedinfo.schedule_now=true' -H 'Content-Type:application/json; charset=UTF-8' -d '{"_output_location":"LOCAL","_object":"db_objects","all_object_types_supported_in_version":"2.5","_encoding":"ROWJSON"}'

OUTPUT
"scheduledtask/b25lLnF1ZXVlZF90YXNrJDc4MC4w:780/WAITING_EXECUTION"

LOG
2018-09-26T13:53:07+00:00 local6 singlegridmaster.local.info httpd[]: notice 2018-09-26 13:53:07.524Z [Last,\040First,\040CERT]: Login_Allowed - - to=AdminConnector ip=10.1.1.20 auth=LOCAL group=admin-group apparently_via=API
2018-09-26T13:53:13+00:00 local6 singlegridmaster.local.info httpd[]: notice 2018-09-26 13:53:13.192Z [Last,\040First,\040CERT]: Login_Allowed - - to=AdminConnector ip=10.1.1.20 auth=LOCAL group=admin-group apparently_via=API

INPUT
curl -k -E ./apilogin.crt.pem --key apilogin.key.pem -X GET 'https://10.0.0.1/wapi/v2.7/scheduledtask'

OUTPUT
[
    {
        "_ref": "scheduledtask/b25lLnF1ZXVlZF90YXNrJDc4MC4w:780/WAITING_EXECUTION",
        "approval_status": "NONE",
        "execution_status": "WAITING_EXECUTION",
        "task_id": 780
    }
]

LOG
2018-09-26T13:53:13+00:00 local6 singlegridmaster.local.info httpd[]: notice 2018-09-26 13:53:13.208Z [Last,\040First,\040CERT]: Sched:780 Called - WAPIRead: Args return_fields=NULL,encoding="ROWJSON",object_type="AllChangedObjects",search_args_all_object_types_supported_in_version="2.5",max_results=-1000,location="LOCAL"
2018-09-26T13:53:13+00:00 local6 singlegridmaster.local.info httpd[]: notice 2018-09-26 13:53:13.208Z [Last,\040First,\040CERT]: Sched:780 Created ScheduledTask 780: Set scheduled_time=NULL,submit_time=2018-09-26 13:53:13.201Z,submitter="Last, First, CERT",type="SCHEDULED",execution_status="WAITING_EXECUTION"

INPUT
curl -k -E ./apilogin.crt.pem --key apilogin.key.pem -X GET 'https://10.0.0.1/wapi/v2.7/scheduledtask'

OUTPUT
[
    {
        "_ref": "scheduledtask/b25lLnF1ZXVlZF90YXNrJDc4MC4w:780/FAILED",
        "approval_status": "NONE",
        "execution_status": "FAILED",
        "task_id": 780
    }
]

LOG
2018-09-26T13:53:17+00:00 local6 singlegridmaster.local.info httpd[]: notice 2018-09-26 13:53:17.045Z [Last,\040First,\040CERT]: Login_Allowed - - to=AdminConnector ip=10.1.1.20 auth=LOCAL group=admin-group apparently_via=API
2018-09-26T13:53:29+00:00 local6 singlegridmaster.local.info python[]: notice 2018-09-26 13:53:29.339Z [Last,\040First,\040CERT]: Modified ScheduledTask 780 category=internal error='.reqcache': Changed execution_status:"WAITING_EXECUTION"->"FAILED"

INPUT
curl -k -E ./apilogin.crt.pem --key apilogin.key.pem -X POST 'https://10.0.0.1/wapi/v2.7/fileop?_function=get_file_url' -H "Content-Type:application/json" -d '{"task_id":780}'

OUTPUT
{ "Error": "AdmConProtoError: The specified scheduled task is not completed, operation not allowed.",
  "code": "Client.Ibap.Proto",
  "text": "The specified scheduled task is not completed, operation not allowed."
}

At this point the task stays listed in Administration -> Workflow -> Task Manager with Approval Status of "Not Applicable" and Execution Status "Failed" until I delete the task through the GUI.

I have searched the Infoblox site for "internal error='.reqcache'" without success. 

Any ideas?

[#2]

I've run into the exact same issue as this, we're on 8.1.4-358341 here.

jgrip$ http POST https://ipam.example.com/wapi/v2.6/fileop _function==read _output_location=LOCAL _object=db_objects _encoding=ROWJSON all_object_types_supported_in_version=2.5
HTTP/1.1 500 Internal Server Error
Cache-Control: no-cache, no-store
Connection: close
Content-Type: application/json
Date: Tue, 30 Oct 2018 14:42:19 GMT
Pragma: no-cache
Transfer-Encoding: chunked
set-cookie: ibapauth="ip=10.1.1.1,client=API,group=group,ctime=1540910544,timeout=28800,mtime=1540910544,su=1,auth=RADIUS,user=jgrip,xxxx"; httponly; Path=/; secure

{
    "Error": "AdmConError: None ('.reqcache')",
    "code": "Server.Ibap.Internal",
    "text": "Internal Error"
}

Tried with both LOCAL and FILE_DISTRIBUTION for the location, same result.

No solution as of yet