Usakana Unfortunately, downgrading and importing a skeleton to 2.1.27 after working with a newer version is absolutely not recommended. Downgrading may result in loss of information and may be a waste of work. Since 2.1.27 is already a 9 year old version, I am afraid we can offer little or almost no support. Please consider upgrading the version of Spine you are using for your project.

Usakana If you really want to try to set a skeleton with a newer version then rollback it to 2.1.27, you can try the procedure described in the following thread:
https://esotericsoftware.com/forum/d/6534-spine-editor-and-runtime-version-management
The use case envisioned in the JsonRollback tool is "when you want to downgrade if you accidentally upgrade your version of Spine", so I want to reiterate that we do not recommend incorporating this into your workflow.

Usakana Hmmm, that is weird... Can you access the following link?:
Spine editor and runtime version management