Steps to reproduce:

1. Download and open attached project
2. Press play
3. Observe as the cube mesh gets corrupted

Note: Once this is done, the mesh(in this case "cube") stays corrupted until you relaunch the project.
Note: Adding a skinned mesh renderer of the same mesh after running will also add a corrupted mesh.

Steps to recreate on a new gameobject with a different mesh:

1. Create a new gameobject of a currently not corrupted mesh (ex. sphere)
2. Add Skinned Mesh Renderer component
3. Remove default Mesh Renderer component
4. Add the User's mesh corrupt script to gameobject
5. Press play
6. Observe as the rendered mesh gets corrupted - Added a video in last edit

Note: User's script is based on https://docs.unity3d.com/ScriptReference/Mesh-bindposes.html, except it is modified to to add bones on a created object,rather than a new one.

Expected result: bones are added normally
Actual result: mesh gets corrupted

Reproduced on 5.2.3f1, 5.3.6f1 5.4.1f1, 5.4.1p3, 5.5.0b5