When customer tried to add a new generic system for one of leaf device, that leaf device got unassigned from its blueprint.

1. Apstra version - 4.1.1
2. Device unassigned from BP
3. Deploy mode and serial number of the device will get cleared in the staged section.
4. In the managed device section user can the device state as "OOS-READY" instead of "IS-ACTIVE"

Device seems to be removed when generic system is attached into the unused port for non-default transformation because of AOS-33756 bug. When customer executes adding generic system with non-default transformation into the unused port in the leaf device or changes speed of link, this issue can occur in 4.1.0 and 4.1.1 running Apstra. 

Workaround as indicated in the release notes of 4.1.1:

After any fabric or flexible fabric expansion operation on a managed system, please do not immediately commit. Check the system's deploy mode and, if unset, please set it to "deploy" again, then also reassign the device that was originally assigned to the managed system.

https://supportportal.juniper.net/s/article/Juniper-Apstra-Software-Release-Notification-for-Juniper-Apstra-Version-4-1-1?language=en_US

There are several cases to hit this bug, not only new GS creation: please see AOS 33756 for reference.

A variety of fabric expansion operations or flexible fabric expansion operations on a node can result in the node being unassigned from its blueprint and its deploy_mode cleared. Examples include:

• Addition of a new generic system to a managed system's port that does not belong to the default transformation.
• If two link speed changes are made to a managed system in the same commit, and the speeds are swapped symmetrically (e.g. 10G -> 1G for the first link and 1G -> 10G for the second link), the specific system can be unassigned from the blueprint.
• Other cases where changes have to be effected to the interface map blueprint node used by the system undergoing fe or ffe expansion.

Example as in the below screenshot: Deply mode changed to 'not set' and s/n as 'not assigned'