martinlu Thank you for sending the repro project! I have confirmed I can reproduce the problem and this appears to be like a bug when using Polygons packing when exporting from the Spine editor.
The reason I think this is because after I checked your Unity project, I tried to repack the textures of your skeleton using the example scene included in the spine-unity runtime, and I was able to reproduce the same problem there. So there seems to be no problem with the script or the implementation.
Then I imported your skeleton data into Spine 4.1.24 and re-exported the skeleton with the Packing option set to Rectangles and re-imported it into the Unity project, the repacking problem did not occur. However, when I set it to Polygons, the repacking problem occurred again.
Unfortunately, Harald, who is in charge of spine-unity, will not be available until January 8th for the winter holidays, so so we are afraid you will have to wait until this issue is fixed, but I think we should be able to work around it at least once by changing the packing method. Could you try it?
