When Creating shaders in mono everything is fine accept when using mesh.parentbone.transform ill use a basic diffuse shader as a example.
effect.Parameters["World"].SetValue(world * mesh.ParentBone.Transform);
If you process a model using a XNA built file within monogame its fine:
But if you use MonoGame Pipline to build the same model you get this:
Now you might think the model is the issue not mono, well when you remove the ParentBone.Transform you get this with the mono built object:
So the issue has soemthign to do with MonoGame Pipline and its Bones