Imershard Thank you for sending your Spine project files! There is nothing wrong with the output image at all. This is because it was exported as an atlas page. To find out what the atlas itself is, see the "Texture packing" page in the Spine User Guide.:
https://esotericsoftware.com/spine-texture-packer#Texture-packing

Even if the images used for the skeleton are rotated or positioned differently on the atlas page, the Spine runtimes will reproduce the correct appearance based on the information provided in the atlas file.
For example, the textures you sent me that look like the branches are arranged in pieces will look correct like this when loaded in Skeleton Viewer:

However, regardless of the texture, I was concerned that your JSON file was exported in 4.0 format from 4.1.24.
If you were trying to downgrade the skeleton and exported it that way, no problem, but if the version of the runtime you are using in your game project is 4.0 and you exported it with the 4.0 format to match, it will not work. The major and minor version for the Spine editor used to export JSON or binary data must always match the Spine Runtimes version. If not, the Spine Runtimes will not be able to read the data. This dependency is very important.
Exporting to older versions is only intended as a last resort to partially recover work if a project was inadvertently saved with a newer version of Spine. Therefore, if the runtime version of your project is 4.0, you must use Spine 4.0 to create your animations. If you want to continue using Spine 4.1, please upgrade the runtime you are using for your project to 4.1.

See the Versioning page for details:
https://esotericsoftware.com/spine-versioning#Synchronizing-versions