There is a 2nd Edition of the "Troubleshooting Cisco Application Centric Infrastructure" which has been mainly available via PDF since the beginning of 2020:
"Troubleshooting Cisco Application Centric Infrastructure, 2nd Edition" PDF
There is some info missing in how you're creating and sending the request, as well as what roles/privileges you have assigned to the user you're testing with.
With that said, the information you sent below from the API documenta...
For operStateReason: notConnect you will want to look into the physical cabling of the peer device as well as speed/negotiation policies tied to the interface in question.
As for the above response, you will want to be more concern...
Please take a moment to view the following white paper on endpoint learning behaviors in ACI:
There are some considerations when it comes to ACI and Spanning Tree. Whether or not BPDUs pass from one leaf to another within the same BD will depend on your configuration. Please see the following note from this guide:
A Note About...
L3outs do not partake in endpoint learning in the manner that EPGs with static bindings do. At first thought, I would not think your l3out config is having bearing on IP movement.
If you are saying that you have hits when running "less...