Let's consider that there is a function named: Function_name
   Press mouse right click on the name of the function and go to 'Rename "function name"...' menu. 
   In my case, the Rename window in launched, but the function can't be found.
 
   This seems to happen because the name of the function start with upper case letter. If the function name will be changed to "function_name", then everything works, but it doesn't work if an upper case letter is in the name of the function, for example: "function_Name".

   This problem could be because the Rename action, when it is launched, it convert all upper case letters from function name to lower case letters, when it is launched. I saw this in the Rename window, at "New name" input field, when the name of the function is converted to lower case letters

   Thanks a lot!