When renaming the torrent from NAME1 to Name1 (only the letter case), the client says "error renaming 80".
The client settings contain "file allocation - Full Pre-Write". When the torrent is launched, it starts creating a file "filename1" renaming it to "filename2" at that moment results in an error saying "unable to open file". Is it possible to make the renaming only after the files are fully created?

there is a very simple workaround for this. The problem is windows filenames are case insensitive. In windows, NAME1 = Name1

Tixati writes the new file before deleting the old so their is a conflict (file already exists) resulting in error renaming 80

So simple change the case as you wish then add a "+" (or any other valid character) to the filename. After this saves, go back and rename it again, this time deleting the "+"

NAME1.mp3 > Name1+.mp3 > Name1.mp3