ASM Export JSON - size Limit ?

Hello,
I'm trying to export an ASM Policy in json format through API

I'm using theses Steps:
- Start the export:

https://{hostname}/mgmt/tm/asm/tasks/export-policy

{
"format": "json",

"filename": "exported_file.json",

"minimal": true,

"policyReference": {

"link": "https://localhost/mgmt/tm/asm/policies/{policyID}"

}

}

- Waiting for the export to end

- Download The export
https://{hostname}//mgmt/tm/asm/file-transfer/downloads/exported_file.json

The downloaded file is imcomplete, truncated and not usable if I try to import it 
Not sure if it the cause but the size of the file is 1Mo

While if I export it manually through GUI it's 1,3Mo sized 
Also I've already modified the max_json_policy_size to 5Mo in the
Security  ››  Options : Application Security : Advanced Configuration : System Variables
Because I had issues when importing the same policie.

Is there some kind of limit for export ?