herolulu Thank you for creating this new thread!

First of all, let me clarify some terminology: the outermost edge of a mesh attachment is called the “mesh hull”.
Please note that there are attachments in Spine called "bounding box attachments", so if you call a mesh hull a bounding box, it will be confused with that one. (I assumed you were probably talking about mesh hulls, as the bounding box attachment did not exist in the Spine project you attached.)

The vertices that form the hull of the mesh cannot be placed outside the image size, so if you want to place the vertices further out, add padding on all four sides of the image.
When resizing an image, it is recommended to keep the ratio as unchanged as possible, because if the ratio changes, the mesh vertices may have to be re-set.
If a change in image size is detected, the following dialogue is displayed:

Select Keep size and press OK. You will then see that padding has been added to the four sides when you try to edit the mesh attachment again, as shown below (Unchecking Deformed shows this.):

However, in the case of this mesh, there is a slightly special situation: the triangles in the area shown in the attached image are connected in an unusual way (the dotted lines, representing triangles, are drawn outside the mesh hull.):

If such unusual triangle connections are created, you should carefully search for the vertices that may be causing the problem, remove them and create new vertices. In this case, the fix was achieved by following the steps shown in the video below:

I hope this will help you.

herolulu I would advise you to recreate this mesh from scratch to avoid future problems. Make sure to have "Deformed" checked while creating it again.
https://esotericsoftware.com/spine-meshes/#Deformed

herolulu Unfortunately, copy-paste of weights is not available in your case because you are using Spine 4.1. Copy-paste of weights has been available since 4.2.

If you want to reuse weights set on other meshes with features up to 4.1, you can do so by duplicating an existing mesh attachment, editing the image path, and replacing it with another image. However, this is not very efficient for parts with significantly different shapes, so it may be faster to create a new mesh attachment and set the weights using a weight brush mode such as Replace.