In the documentation page:
[Level Instancing in Unreal Engine | Unreal Engine 5.0 Documentation|https://docs.unrealengine.com/5.0/en-US/level-instancing-in-unreal-engine/]
it is mentioned that:
But in both UE5.0 and 5.1, when user edit one instance of the packed level blueprint and commit it, or directly edit the blueprint itself, other instances in the level will update immediately. It is not as expected.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-171087 in the post.