Description of the Issue

The issue seems to have been introduced by the version 7 of Notepad++.

If more than two files are open at once, and the "Find All in All Opened Documents " function is invoked, accented characters are not matched in some of the files.

The screenshot displays the result of looking for the "í" character (lowercase letter i with acute accent) in three small files, where all of them do contain at least one occurrence of that character.

Steps to Reproduce the Issue

1. Open the three attached files.
2. Try to find the "í" character in all of them by means of the Find All in All Opened Documents function.

Expected Behavior

Matches in all three files should have been found.

Actual Behavior

Only matches in the first and the third file have been found.

o1.txt
o2.txt
o3.txt

Debug Information

Notepad++ v7.8.9 (64-bit)
Build time : Jul 15 2020 - 20:31:49
Path : C:_bin\npp\notepad++.exe
Admin mode : OFF
Local Conf mode : ON
OS Name : Windows 10 Home (64-bit)
OS Version : 1909
OS Build : 18363.1082
Current ANSI codepage : 1250
Plugins : mimeTools.dll NppConverter.dll NppExport.dll