I doubt I can say much that you didn't already try so FWIW
By deleting stuff and saving a new copy every time, you should be able to "scale it down" until it works.
Look at what shadows are overwritten and remove the overwrites.
Remove one plugin at a time.
Maybe before any of that; peek with the inspector tool to see if there's some styling that somehow blocks the edit buttons.
Frustrating.
<:-)