Description of the Issue

Creating the clone of a file in the second view creates a possibly different file in the two views, if changes are added to two views separately. You can't then save any of the two views, without loosing the changes in the other view.
This looks to happen when after cloning you close/reopen the application and make different changes in the left and right views: changes in the right view aren't replicated in the left one and vice versa. Adding many changes you end up with two different versions of the same file, very hard to merge.

Steps to Reproduce the Issue

1. Open a (long) text file in the main view
2. Right click on file name tab and "Clone to other view"
3. Make a few changes in left pane, you'll see them appear in right pane
4. Make a few changes in right pane, still they will be updated in left one
5. Close Notepad++ with the main window close button, without saving anything
6. Reopen Notepad++, changes are apparently preserved
7. Any change that you'll make from now on on left or right pane won't be replicated in the other one: file name is still the same, but you're working on two different copies (not cloned, not linked anymore)

Expected Behavior

I just expected that reopening the application the link between the two windows is preserved, while it's not, even though they claim to be the same file on-disk

Actual Behavior

I ended up with left pane having only the changes made in it, after the restart of the application. The same happens to right pane, and I can't track anymore all the changes as they're logged separately.

Debug Information

Notepad++ v8.1.1 (32-bit)
Build time : Jul 1 2021 - 14:04:28
Path : C:\Program Files (x86)\Notepad++\notepad++.exe
Command Line :
Admin mode : OFF
Local Conf mode : OFF
Cloud Config : OFF
OS Name : Windows 10 Enterprise (64-bit)
OS Version : 2009
OS Build : 19043.1110
Current ANSI codepage : 1252
Plugins : mimeTools.dll NppConverter.dll NppExport.dll