Cannot save prefab even removed missing script.

I have a prefab which reference to a script original. I removed that script from code. The prefab could not find it show missing prefab.I open the prefab and remove that missing script component.
However, although it is removed from the game object and no longer has the "missing script" component, the prefab still doesn't save.

Using the latest Unity 2019.4.9f1 LTS



update: Nevermind, issue fixed. There are more missing prefab than the reported one.