By changing the PW of a user, you need to type it twice.
If you are in the second field and directly click "save", the password is not stored and an error message says: "Retype new Password: Validation Error: Value is required"
You can circumvent this by first clicking on the white space to exit the 2nd edit field. Then you can click on Save. However, this procedure is not intuitive. 

I was logged in as admin. I do not know if this also happens for normal user that want to change their PW.