timeout exception when submitting task via icontrol

I'm trying to save a UCS archive on our F5s running 13.1.4.1 via icontrol.

When I POST the following JSON to https://ip.addr/mgmt/tm/task/sys/ucs I get a 400 response showing a timeoutexeception

{

"command": "save",

"name": "ucsfilename"

}

This same POST to our other F5s running version 15 work fine. I get a task ID back and use that to change the taskstate to VALIDATING.

Does this work differently on version 13?