Hallo;
I'm using Python/Requests for api call to DNAC.
The same problem described is also from DNAC itself (dna/platform/app/consumer-portal/developer-toolkit/apis).
Edge device is discovered, added to site and provisioned and now ready to insert into the fabric.
If I'm using "Add edge device in SDA Fabric" call with button "Try it":

Response is 200 but error returned:
{
"status": "failed",
"description": "Uknown error happened.",
"executionStatusUrl": "https://172.28.254.100/api/dnacaap/v1/dnacaap/management/execution-status/ee34d318-a152-4fa8-992b-c7fe6affdf51"
}
If I add Edge device "manually" via DNAC web interface "Provision/Fabric/..." this is working normally.
Any suggestion is appreciated.
Best regards,
Branko